diff --git a/Octokit.Reactive/IObservableRepositoriesClient.cs b/Octokit.Reactive/IObservableRepositoriesClient.cs
index ea3a1b8e..7be823b1 100644
--- a/Octokit.Reactive/IObservableRepositoriesClient.cs
+++ b/Octokit.Reactive/IObservableRepositoriesClient.cs
@@ -21,7 +21,7 @@ namespace Octokit.Reactive
         /// <remarks>
         /// The default page size on GitHub.com is 30.
         /// </remarks>
-        /// <exception cref="AuthenticationException">Thrown if the client is not authenticated.</exception>
+        /// <exception cref="AuthorizationException">Thrown if the client is not authenticated.</exception>
         /// <returns>A <see cref="IReadOnlyPagedCollection{Repository}"/> of <see cref="Repository"/>.</returns>
         [SuppressMessage("Microsoft.Design", "CA1024:UsePropertiesWhereAppropriate",
             Justification = "Makes a network request")]
diff --git a/Octokit.Reactive/IObservableSshKeysClient.cs b/Octokit.Reactive/IObservableSshKeysClient.cs
index dd8dab14..7052686e 100644
--- a/Octokit.Reactive/IObservableSshKeysClient.cs
+++ b/Octokit.Reactive/IObservableSshKeysClient.cs
@@ -25,7 +25,7 @@ namespace Octokit.Reactive
         /// <summary>
         /// Retrieves the <see cref="SshKey"/> for the specified id.
         /// </summary>
-        /// <exception cref="AuthenticationException">Thrown if the client is not authenticated.</exception>
+        /// <exception cref="AuthorizationException">Thrown if the client is not authenticated.</exception>
         /// <returns>A <see cref="IReadOnlyPagedCollection{SshKey}"/> of <see cref="SshKey"/>.</returns>
         [SuppressMessage("Microsoft.Design", "CA1024:UsePropertiesWhereAppropriate",
             Justification = "Makes a network request")]
@@ -35,7 +35,7 @@ namespace Octokit.Reactive
         /// Update the specified <see cref="UserUpdate"/>.
         /// </summary>
         /// <param name="key"></param>
-        /// <exception cref="AuthenticationException">Thrown if the client is not authenticated.</exception>
+        /// <exception cref="AuthorizationException">Thrown if the client is not authenticated.</exception>
         /// <returns>A <see cref="User"/></returns>
         IObservable<SshKey> Create(SshKeyUpdate key);
 
@@ -44,7 +44,7 @@ namespace Octokit.Reactive
         /// </summary>
         /// <param name="id"></param>
         /// <param name="key"></param>
-        /// <exception cref="AuthenticationException">Thrown if the client is not authenticated.</exception>
+        /// <exception cref="AuthorizationException">Thrown if the client is not authenticated.</exception>
         /// <returns>A <see cref="User"/></returns>
         IObservable<SshKey> Update(int id, SshKeyUpdate key);
 
@@ -52,7 +52,7 @@ namespace Octokit.Reactive
         /// Update the specified <see cref="UserUpdate"/>.
         /// </summary>
         /// <param name="id">The id of the SSH key</param>
-        /// <exception cref="AuthenticationException">Thrown if the client is not authenticated.</exception>
+        /// <exception cref="AuthorizationException">Thrown if the client is not authenticated.</exception>
         /// <returns>A <see cref="User"/></returns>
         IObservable<Unit> Delete(int id);
     }
diff --git a/Octokit.Reactive/IObservableUsersClient.cs b/Octokit.Reactive/IObservableUsersClient.cs
index 0372e596..8440c1ce 100644
--- a/Octokit.Reactive/IObservableUsersClient.cs
+++ b/Octokit.Reactive/IObservableUsersClient.cs
@@ -18,7 +18,7 @@ namespace Octokit.Reactive
         /// <summary>
         /// Returns a <see cref="User"/> for the current authenticated user.
         /// </summary>
-        /// <exception cref="AuthenticationException">Thrown if the client is not authenticated.</exception>
+        /// <exception cref="AuthorizationException">Thrown if the client is not authenticated.</exception>
         /// <returns>A <see cref="User"/></returns>
         IObservable<User> Current();
 
@@ -26,7 +26,7 @@ namespace Octokit.Reactive
         /// Update the specified <see cref="UserUpdate"/>.
         /// </summary>
         /// <param name="user"></param>
-        /// <exception cref="AuthenticationException">Thrown if the client is not authenticated.</exception>
+        /// <exception cref="AuthorizationException">Thrown if the client is not authenticated.</exception>
         /// <returns>A <see cref="User"/></returns>
         IObservable<User> Update(UserUpdate user);
     }
diff --git a/Octokit.Tests.Integration/UsersClientTests.cs b/Octokit.Tests.Integration/UsersClientTests.cs
index e7eadb67..023e3ff8 100644
--- a/Octokit.Tests.Integration/UsersClientTests.cs
+++ b/Octokit.Tests.Integration/UsersClientTests.cs
@@ -53,7 +53,7 @@ namespace Octokit.Tests.Integration
                     Bio = "UPDATED BIO"
                 };
 
-                var e = await AssertEx.Throws<AuthenticationException>(async 
+                var e = await AssertEx.Throws<AuthorizationException>(async 
                     () => await github.User.Update(userUpdate));
                 Assert.Equal(HttpStatusCode.Unauthorized, e.StatusCode);
             }
@@ -71,7 +71,7 @@ namespace Octokit.Tests.Integration
                     Bio = "UPDATED BIO"
                 };
 
-                var e = await AssertEx.Throws<AuthenticationException>(async 
+                var e = await AssertEx.Throws<AuthorizationException>(async 
                     () => await github.User.Update(userUpdate));
                 Assert.Equal(HttpStatusCode.Unauthorized, e.StatusCode);
             }
diff --git a/Octokit.Tests/Exceptions/ApiValidationExceptionTests.cs b/Octokit.Tests/Exceptions/ApiValidationExceptionTests.cs
new file mode 100644
index 00000000..a6b532ac
--- /dev/null
+++ b/Octokit.Tests/Exceptions/ApiValidationExceptionTests.cs
@@ -0,0 +1,63 @@
+using System.IO;
+using System.Linq;
+using System.Runtime.Serialization.Formatters.Binary;
+using NSubstitute;
+using Octokit.Http;
+using Xunit;
+using Xunit.Extensions;
+
+namespace Octokit.Tests.Exceptions
+{
+    public class ApiValidationExceptionTests
+    {
+        public class TheConstructor
+        {
+            [Fact]
+            public void CreatesGitHubErrorFromJsonResponse()
+            {
+                var response = Substitute.For<IResponse>();
+                response.Body.Returns(@"{""errors"":[{""code"":""custom"",""field"":""key"",""message"":""key is " + 
+                    @"already in use"",""resource"":""PublicKey""}],""message"":""Validation Failed""}");
+
+                var exception = new ApiValidationException(response);
+
+                Assert.Equal("Validation Failed", exception.ApiValidationError.Message);
+                Assert.Equal("key is already in use", exception.ApiValidationError.Errors.First().Message);
+            }
+
+            [Theory]
+            [InlineData("")]
+            [InlineData(null)]
+            [InlineData("{{{{{")]
+            public void CreatesGitHubErrorIfResponseMessageIsNotValidJson(string responseContent)
+            {
+                var response = Substitute.For<IResponse>();
+                response.Body.Returns(responseContent);
+
+                var exception = new ApiValidationException(response);
+
+                Assert.Equal(responseContent, exception.ApiValidationError.Message);
+            }
+
+            [Fact]
+            public void CanPopulateObjectFromSerializedData()
+            {
+                var response = Substitute.For<IResponse>();
+                response.Body.Returns(@"{""errors"":[{""code"":""custom"",""field"":""key"",""message"":""key is " + 
+                    @"already in use"",""resource"":""PublicKey""}],""message"":""Validation Failed""}");
+
+                var exception = new ApiValidationException(response);
+                
+                using (var stream = new MemoryStream())
+                {
+                    var formatter = new BinaryFormatter();
+                    formatter.Serialize(stream, exception);
+                    stream.Position = 0;
+                    var deserialized = (ApiValidationException)formatter.Deserialize(stream);
+                    Assert.Equal("Validation Failed", deserialized.ApiValidationError.Message);
+                    Assert.Equal("key is already in use", exception.ApiValidationError.Errors.First().Message);
+                }
+            }
+        }
+    }
+}
\ No newline at end of file
diff --git a/Octokit.Tests/Http/ConnectionTests.cs b/Octokit.Tests/Http/ConnectionTests.cs
index d6b6a161..13b20e19 100644
--- a/Octokit.Tests/Http/ConnectionTests.cs
+++ b/Octokit.Tests/Http/ConnectionTests.cs
@@ -120,25 +120,46 @@ namespace Octokit.Tests.Http
                 Assert.Equal("user", resp.ApiInfo.AcceptedOauthScopes.First());
             }
 
-            [Theory]
-            [InlineData(HttpStatusCode.Forbidden)]
-            [InlineData(HttpStatusCode.Unauthorized)]
-            public async Task ThrowsAuthenticationExceptionExceptionForAppropriateStatusCodes(HttpStatusCode statusCode)
+            [Fact]
+            public async Task ThrowsAuthorizationExceptionExceptionForUnauthorizedResponse()
             {
                 var httpClient = Substitute.For<IHttpClient>();
-                IResponse<string> response = new ApiResponse<string> { StatusCode = statusCode};
+                IResponse<string> response = new ApiResponse<string> { StatusCode = HttpStatusCode.Unauthorized};
                 httpClient.Send<string>(Args.Request).Returns(Task.FromResult(response));
                 var connection = new Connection(ExampleUri,
                     Substitute.For<ICredentialStore>(),
                     httpClient,
                     Substitute.For<IJsonSerializer>());
 
-                var exception = await AssertEx.Throws<AuthenticationException>(
+                var exception = await AssertEx.Throws<AuthorizationException>(
                     async () => await connection.GetAsync<string>(new Uri("/endpoint", UriKind.Relative)));
 
                 Assert.Equal("You must be authenticated to call this method. Either supply a login/password or an " +
                              "oauth token.", exception.Message);
             }
+
+            [Fact]
+            public async Task ThrowsApiValidationExceptionFor422Response()
+            {
+                var httpClient = Substitute.For<IHttpClient>();
+                IResponse<string> response = new ApiResponse<string>
+                {
+                    StatusCode = (HttpStatusCode)422,
+                    Body = @"{""errors"":[{""code"":""custom"",""field"":""key"",""message"":""key is " +
+                        @"already in use"",""resource"":""PublicKey""}],""message"":""Validation Failed""}"
+                };
+                httpClient.Send<string>(Args.Request).Returns(Task.FromResult(response));
+                var connection = new Connection(ExampleUri,
+                    Substitute.For<ICredentialStore>(),
+                    httpClient,
+                    Substitute.For<IJsonSerializer>());
+
+                var exception = await AssertEx.Throws<ApiValidationException>(
+                    async () => await connection.GetAsync<string>(new Uri("/endpoint", UriKind.Relative)));
+
+                Assert.Equal("Validation Failed", exception.Message);
+                Assert.Equal("key is already in use", exception.ApiValidationError.Errors[0].Message);
+            }
         }
 
         public class TheGetHtmlMethod
diff --git a/Octokit.Tests/Octokit.Tests.csproj b/Octokit.Tests/Octokit.Tests.csproj
index 6d92611b..1a2d582e 100644
--- a/Octokit.Tests/Octokit.Tests.csproj
+++ b/Octokit.Tests/Octokit.Tests.csproj
@@ -52,6 +52,7 @@
   <ItemGroup>
     <Compile Include="Authentication\CredentialsTests.cs" />
     <Compile Include="Clients\SshKeysClientTests.cs" />
+    <Compile Include="Exceptions\ApiValidationExceptionTests.cs" />
     <Compile Include="Helpers\UriExtensionsTests.cs" />
     <Compile Include="Http\ApiConnectionTests.cs" />
     <Compile Include="Clients\AuthorizationsClientTests.cs" />
diff --git a/Octokit/AuthenticationException.cs b/Octokit/AuthenticationException.cs
deleted file mode 100644
index 4de141ff..00000000
--- a/Octokit/AuthenticationException.cs
+++ /dev/null
@@ -1,54 +0,0 @@
-using System;
-using System.Net;
-using System.Runtime.Serialization;
-
-namespace Octokit
-{
-#if !NETFX_CORE
-    [Serializable]
-#endif
-    public class AuthenticationException : Exception
-    {
-        public AuthenticationException()
-        {
-        }
-
-        public AuthenticationException(string message)
-            : base(message)
-        {
-        }
-
-        public AuthenticationException(string message, HttpStatusCode statusCode)
-            : base(message)
-        {
-            StatusCode = statusCode;
-        }
-
-        public AuthenticationException(string message, Exception innerException)
-            : base(message, innerException)
-        {
-        }
-
-        public AuthenticationException(string message, Exception innerException, HttpStatusCode statusCode)
-            : base(message, innerException)
-        {
-            StatusCode = statusCode;
-        }
-
-        public HttpStatusCode StatusCode { get; private set; }
-
-#if !NETFX_CORE
-        protected AuthenticationException(SerializationInfo info, StreamingContext context) : base(info, context)
-        {
-            if (info == null) return;
-            StatusCode = (HttpStatusCode)(info.GetInt32("StatusCode"));
-        }
-
-        public override void GetObjectData(SerializationInfo info, StreamingContext context)
-        {
-            base.GetObjectData(info, context);
-            info.AddValue("StatusCode", StatusCode);
-        }
-#endif
-    }
-}
diff --git a/Octokit/Clients/UsersClient.cs b/Octokit/Clients/UsersClient.cs
index e210b4af..a8e67a3c 100644
--- a/Octokit/Clients/UsersClient.cs
+++ b/Octokit/Clients/UsersClient.cs
@@ -36,7 +36,7 @@ namespace Octokit.Clients
         /// <summary>
         /// Returns a <see cref="User"/> for the current authenticated user.
         /// </summary>
-        /// <exception cref="AuthenticationException">Thrown if the client is not authenticated.</exception>
+        /// <exception cref="AuthorizationException">Thrown if the client is not authenticated.</exception>
         /// <returns>A <see cref="User"/></returns>
         public async Task<User> Current()
         {
@@ -47,7 +47,7 @@ namespace Octokit.Clients
         /// Update the specified <see cref="UserUpdate"/>.
         /// </summary>
         /// <param name="user"></param>
-        /// <exception cref="AuthenticationException">Thrown if the client is not authenticated.</exception>
+        /// <exception cref="AuthorizationException">Thrown if the client is not authenticated.</exception>
         /// <returns>A <see cref="User"/></returns>
         public async Task<User> Update(UserUpdate user)
         {
diff --git a/Octokit/Exceptions/ApiException.cs b/Octokit/Exceptions/ApiException.cs
new file mode 100644
index 00000000..9085c0a3
--- /dev/null
+++ b/Octokit/Exceptions/ApiException.cs
@@ -0,0 +1,58 @@
+using System;
+using System.Net;
+using System.Runtime.Serialization;
+
+namespace Octokit
+{
+#if !NETFX_CORE
+    [Serializable]
+#endif
+    public class ApiException : Exception
+    {
+        public ApiException()
+        {
+        }
+
+        public ApiException(HttpStatusCode statusCode)
+        {
+            StatusCode = statusCode;
+        }
+
+        public ApiException(string message) : base(message)
+        {
+        }
+
+        public ApiException(string message, Exception innerException)
+            : base(message, innerException)
+        {
+        }
+
+        public ApiException(string message, Exception innerException, HttpStatusCode statusCode)
+            : base(message, innerException)
+        {
+            StatusCode = statusCode;
+        }
+
+        public ApiException(string message, HttpStatusCode statusCode) : base(message)
+        {
+            StatusCode = statusCode;
+        }
+
+        public HttpStatusCode StatusCode { get; private set; }
+
+#if !NETFX_CORE
+        protected ApiException(SerializationInfo info, StreamingContext context)
+            : base(info, context)
+        {
+            if (info == null) return;
+            StatusCode = (HttpStatusCode)(info.GetInt32("HttpStatusCode"));
+        }
+
+        public override void GetObjectData(SerializationInfo info, StreamingContext context)
+        {
+            base.GetObjectData(info, context);
+            info.AddValue("HttpStatusCode", StatusCode);
+        }
+#endif
+    }
+}
diff --git a/Octokit/Exceptions/ApiValidationException.cs b/Octokit/Exceptions/ApiValidationException.cs
new file mode 100644
index 00000000..d9b1ed99
--- /dev/null
+++ b/Octokit/Exceptions/ApiValidationException.cs
@@ -0,0 +1,87 @@
+using System;
+using System.Diagnostics.CodeAnalysis;
+using System.Runtime.Serialization;
+using Octokit.Http;
+
+namespace Octokit
+{
+    /// <summary>
+    ///     Represents a validation exception (HTTP STATUS: 422) returned from the API.
+    /// </summary>
+#if !NETFX_CORE
+    [Serializable]
+#endif
+    public class ApiValidationException : ApiException
+    {
+        // This needs to be hard-coded for translating GitHub error messages.
+        static readonly IJsonSerializer _jsonSerializer = new SimpleJsonSerializer();
+
+        public ApiValidationException()
+        {
+        }
+
+        public ApiValidationException(string message)
+            : base(message)
+        {
+        }
+
+        public ApiValidationException(string message, Exception innerException)
+            : base(message, innerException)
+        {
+        }
+
+        public ApiValidationException(IResponse response)
+            : this(response, null)
+        {
+        }
+
+        public ApiValidationException(IResponse response, Exception innerException)
+            : this(GetApiErrorFromExceptionMessage(response), innerException)
+        {
+        }
+
+        protected ApiValidationException(ApiError apiValidationError, Exception innerException)
+            : base(apiValidationError != null ? apiValidationError.Message : "An API error occurred", innerException)
+        {
+            ApiValidationError = apiValidationError;
+        }
+
+#if !NETFX_CORE
+        protected ApiValidationException(SerializationInfo info, StreamingContext context)
+            : base(info, context)
+        {
+            ApiValidationError = GetApiErrorFromExceptionMessage(info.GetString("ApiValidationError"));
+        }
+
+        public override void GetObjectData(SerializationInfo info, StreamingContext context)
+        {
+            base.GetObjectData(info, context);
+
+            info.AddValue("ApiValidationError", _jsonSerializer.Serialize(ApiValidationError));
+        }
+#endif
+
+        public ApiError ApiValidationError { get; private set; }
+
+        static ApiError GetApiErrorFromExceptionMessage(IResponse response)
+        {
+            string responseBody = response != null ? response.Body : null;
+            return GetApiErrorFromExceptionMessage(responseBody);
+        }
+
+        [SuppressMessage("Microsoft.Design", "CA1031:DoNotCatchGeneralExceptionTypes")]
+        static ApiError GetApiErrorFromExceptionMessage(string responseContent)
+        {
+            try
+            {
+                if (responseContent != null)
+                    return _jsonSerializer.Deserialize<ApiError>(responseContent) ?? new ApiError { Message = responseContent };
+            }
+            catch (Exception)
+            {
+            }
+
+            return new ApiError { Message = responseContent };
+        }
+    }
+}
diff --git a/Octokit/Exceptions/AuthorizationException.cs b/Octokit/Exceptions/AuthorizationException.cs
new file mode 100644
index 00000000..55e3e616
--- /dev/null
+++ b/Octokit/Exceptions/AuthorizationException.cs
@@ -0,0 +1,36 @@
+using System;
+using System.Net;
+using System.Runtime.Serialization;
+
+namespace Octokit
+{
+    /// <summary>
+    /// Exception thrown when we receive an HttpStatusCode.Unauthorized (HTTP 401) response.
+    /// </summary>
+#if !NETFX_CORE
+    [Serializable]
+#endif
+    public class AuthorizationException : ApiException
+    {
+        public AuthorizationException()
+        {
+        }
+
+        public AuthorizationException(string message)
+            : base(message, null, HttpStatusCode.Unauthorized)
+        {
+        }
+
+        public AuthorizationException(string message, Exception innerException)
+            : base(message, innerException, HttpStatusCode.Unauthorized)
+        {
+        }
+
+#if !NETFX_CORE
+        protected AuthorizationException(SerializationInfo info, StreamingContext context)
+            : base(info, context)
+        {
+        }
+#endif
+    }
+}
diff --git a/Octokit/GitHubModels.cs b/Octokit/GitHubModels.cs
index 4d6b00f5..8d0895de 100644
--- a/Octokit/GitHubModels.cs
+++ b/Octokit/GitHubModels.cs
@@ -1,4 +1,5 @@
 using System;
+using System.Collections.Generic;
 using System.Diagnostics.CodeAnalysis;
 using System.Text;
 using System.Threading.Tasks;
@@ -452,4 +453,24 @@ namespace Octokit
 
         public bool Primary { get; set; }
     }
+
+    public class ApiError
+    {
+        public string Message { get; set; }
+
+        // TODO: This ought to be an IReadOnlyList<ApiErrorDetail> but we need to add support to SimpleJson for that.
+        [SuppressMessage("Microsoft.Usage", "CA2227:CollectionPropertiesShouldBeReadOnly")]
+        public IList<ApiErrorDetail> Errors { get; set; }
+    }
+
+    public class ApiErrorDetail
+    {
+        public string Message { get; set; }
+
+        public string Code { get; set; }
+
+        public string Field { get; set; }
+
+        public string Resource { get; set; }
+    }
 }
diff --git a/Octokit/Http/Connection.cs b/Octokit/Http/Connection.cs
index 1fd4c589..f2d535ba 100644
--- a/Octokit/Http/Connection.cs
+++ b/Octokit/Http/Connection.cs
@@ -176,13 +176,28 @@ namespace Octokit.Http
 
         static void HandleErrors(IResponse response)
         {
-            if (response.StatusCode == HttpStatusCode.Unauthorized || response.StatusCode == HttpStatusCode.Forbidden)
-                throw new AuthenticationException("You must be authenticated to call this method. Either supply a " +
-                    "login/password or an oauth token.", response.StatusCode);
+            if (response.StatusCode == HttpStatusCode.Unauthorized)
+                throw new AuthorizationException("You must be authenticated to call this method. Either supply a " +
+                    "login/password or an oauth token.");
+
+            if (response.StatusCode == HttpStatusCode.Forbidden)
+            {
+                throw new ApiException("Request Forbidden", response.StatusCode);
+            }
 
             if (response.StatusCode == HttpStatusCode.RequestTimeout)
             {
-                throw new WebException("Request Timed Out", WebExceptionStatus.Timeout);
+                throw new ApiException("Request Timed Out", response.StatusCode);
+            }
+
+            if ((int)response.StatusCode == 422)
+            {
+                throw new ApiValidationException(response);
+            }
+
+            if ((int)response.StatusCode >= 400)
+            {
+                throw new ApiException(response.Body, response.StatusCode);
             }
         }
     }
diff --git a/Octokit/IRepositoriesClient.cs b/Octokit/IRepositoriesClient.cs
index b417028b..347e1ef8 100644
--- a/Octokit/IRepositoriesClient.cs
+++ b/Octokit/IRepositoriesClient.cs
@@ -21,7 +21,7 @@ namespace Octokit
         /// <remarks>
         /// The default page size on GitHub.com is 30.
         /// </remarks>
-        /// <exception cref="AuthenticationException">Thrown if the client is not authenticated.</exception>
+        /// <exception cref="AuthorizationException">Thrown if the client is not authenticated.</exception>
         /// <returns>A <see cref="IReadOnlyPagedCollection{Repository}"/> of <see cref="Repository"/>.</returns>
         [SuppressMessage("Microsoft.Design", "CA1024:UsePropertiesWhereAppropriate",
             Justification = "Makes a network request")]
diff --git a/Octokit/ISshKeysClient.cs b/Octokit/ISshKeysClient.cs
index c94aa2f3..ec4eb68e 100644
--- a/Octokit/ISshKeysClient.cs
+++ b/Octokit/ISshKeysClient.cs
@@ -24,7 +24,7 @@ namespace Octokit
         /// <summary>
         /// Retrieves the <see cref="SshKey"/> for the specified id.
         /// </summary>
-        /// <exception cref="AuthenticationException">Thrown if the client is not authenticated.</exception>
+        /// <exception cref="AuthorizationException">Thrown if the client is not authenticated.</exception>
         /// <returns>A <see cref="IReadOnlyPagedCollection{SshKey}"/> of <see cref="SshKey"/>.</returns>
         [SuppressMessage("Microsoft.Design", "CA1024:UsePropertiesWhereAppropriate",
             Justification = "Makes a network request")]
@@ -34,7 +34,7 @@ namespace Octokit
         /// Update the specified <see cref="UserUpdate"/>.
         /// </summary>
         /// <param name="key"></param>
-        /// <exception cref="AuthenticationException">Thrown if the client is not authenticated.</exception>
+        /// <exception cref="AuthorizationException">Thrown if the client is not authenticated.</exception>
         /// <returns>A <see cref="User"/></returns>
         Task<SshKey> Create(SshKeyUpdate key);
 
@@ -43,7 +43,7 @@ namespace Octokit
         /// </summary>
         /// <param name="id"></param>
         /// <param name="key"></param>
-        /// <exception cref="AuthenticationException">Thrown if the client is not authenticated.</exception>
+        /// <exception cref="AuthorizationException">Thrown if the client is not authenticated.</exception>
         /// <returns>A <see cref="User"/></returns>
         Task<SshKey> Update(int id, SshKeyUpdate key);
 
@@ -51,7 +51,7 @@ namespace Octokit
         /// Update the specified <see cref="UserUpdate"/>.
         /// </summary>
         /// <param name="id">The id of the SSH key</param>
-        /// <exception cref="AuthenticationException">Thrown if the client is not authenticated.</exception>
+        /// <exception cref="AuthorizationException">Thrown if the client is not authenticated.</exception>
         /// <returns>A <see cref="User"/></returns>
         Task Delete(int id);
     }
diff --git a/Octokit/IUsersClient.cs b/Octokit/IUsersClient.cs
index ed6a9cd1..824a4325 100644
--- a/Octokit/IUsersClient.cs
+++ b/Octokit/IUsersClient.cs
@@ -17,7 +17,7 @@ namespace Octokit
         /// <summary>
         /// Returns a <see cref="User"/> for the current authenticated user.
         /// </summary>
-        /// <exception cref="AuthenticationException">Thrown if the client is not authenticated.</exception>
+        /// <exception cref="AuthorizationException">Thrown if the client is not authenticated.</exception>
         /// <returns>A <see cref="User"/></returns>
         Task<User> Current();
 
@@ -25,7 +25,7 @@ namespace Octokit
         /// Update the specified <see cref="UserUpdate"/>.
         /// </summary>
         /// <param name="user"></param>
-        /// <exception cref="AuthenticationException">Thrown if the client is not authenticated.</exception>
+        /// <exception cref="AuthorizationException">Thrown if the client is not authenticated.</exception>
         /// <returns>A <see cref="User"/></returns>
         Task<User> Update(UserUpdate user);
 
diff --git a/Octokit/Octokit.csproj b/Octokit/Octokit.csproj
index 887fc4b6..dd4104b5 100644
--- a/Octokit/Octokit.csproj
+++ b/Octokit/Octokit.csproj
@@ -77,6 +77,7 @@
     </Reference>
   </ItemGroup>
   <ItemGroup>
+    <Compile Include="Exceptions\ApiException.cs" />
     <Compile Include="ApiExtensions.cs" />
     <Compile Include="Clients\ApiClient.cs" />
     <Compile Include="Clients\AuthorizationsClient.cs" />
@@ -86,6 +87,7 @@
     <Compile Include="Authentication\AnonymousAuthenticator.cs" />
     <Compile Include="Authentication\Authenticator.cs" />
     <Compile Include="Clients\SshKeysClient.cs" />
+    <Compile Include="Exceptions\ApiValidationException.cs" />
     <Compile Include="Helpers\CollectionExtensions.cs" />
     <Compile Include="Helpers\Net45CompatibilityShim.cs" />
     <Compile Include="Helpers\UriExtensions.cs" />
@@ -119,7 +121,7 @@
     </Compile>
     <Compile Include="Http\ApiResponse.cs" />
     <Compile Include="Http\IJsonSerializer.cs" />
-    <Compile Include="AuthenticationException.cs" />
+    <Compile Include="Exceptions\AuthorizationException.cs" />
     <Compile Include="Http\SimpleJsonSerializer.cs" />
     <Compile Include="Authentication\TokenAuthenticator.cs">
       <SubType>Code</SubType>
diff --git a/Octokit/OctokitRT.csproj b/Octokit/OctokitRT.csproj
index c9654279..3e9254aa 100644
--- a/Octokit/OctokitRT.csproj
+++ b/Octokit/OctokitRT.csproj
@@ -113,6 +113,9 @@
     <Compile Include="Clients\RepositoriesClient.cs" />
     <Compile Include="Clients\SshKeysClient.cs" />
     <Compile Include="Clients\UsersClient.cs" />
+    <Compile Include="Exceptions\ApiException.cs" />
+    <Compile Include="Exceptions\ApiValidationException.cs" />
+    <Compile Include="Exceptions\AuthorizationException.cs" />
     <Compile Include="Helpers\CollectionExtensions.cs" />
     <Compile Include="Helpers\UriExtensions.cs" />
     <Compile Include="Http\ApiConnection.cs" />
@@ -138,7 +141,6 @@
     </Compile>
     <Compile Include="Http\ApiInfo.cs" />
     <Compile Include="Http\IJsonSerializer.cs" />
-    <Compile Include="AuthenticationException.cs" />
     <Compile Include="Http\SimpleJsonSerializer.cs" />
     <Compile Include="Helpers\Ensure.cs" />
     <Compile Include="GitHubClient.cs" />