diff --git a/AFNetworking/AFHTTPRequestOperation.m b/AFNetworking/AFHTTPRequestOperation.m
index 571d918..b7d72a3 100644
--- a/AFNetworking/AFHTTPRequestOperation.m
+++ b/AFNetworking/AFHTTPRequestOperation.m
@@ -96,7 +96,28 @@
                                                     success:(void (^)(id object))success 
                                                     failure:(void (^)(NSHTTPURLResponse *response, NSError *error))failure
 {
-    return nil;
+    AFHTTPRequestOperation *operation = [[[self alloc] initWithRequest:urlRequest] autorelease];
+    operation.completionBlock = ^ {
+        if ([operation isCancelled]) {
+            return;
+        }
+        
+        if (operation.error) {
+            if (failure) {
+                dispatch_async(dispatch_get_main_queue(), ^(void) {
+                    failure(operation.response, operation.error);
+                });
+            }
+        } else {
+            if (success) {
+                dispatch_async(dispatch_get_main_queue(), ^(void) {
+                    success(operation.responseData);
+                });
+            }
+        }
+    };
+    
+    return operation;
 }        
 
 @end