Dear members, I am facing a problem of -[NSConcreteMutableData release]: message sent to deallocated instance, i have attached my sample code as well. - (IBAction)uploadImage { NSString *urlString = @"http://192.168.1.108/iphoneimages/uploadfile.php?userid=1&charid=23&msgid=3"; //if(FALSE) for (int i=0; i<[imgArray count]; i++) { // setting up the request object now NSMutableURLRequest *request = [[NSMutableURLRequest alloc] init]; [request setURL:[NSURL URLWithString:urlString]]; [request setHTTPMethod:@"POST"]; /* add some header info now we always need a boundary when we post a file also we need to set the content type You might want to generate a random boundary.. this is just the same as my output from wireshark on a valid html post */ NSString *boundary = [NSString stringWithString:@"---------------------------14737809831466499882746641449"]; NSString *contentType = [NSString stringWithFormat:@"multipart/form-data; boundary=%@",boundary]; [request addValue:contentType forHTTPHeaderField: @"Content-Type"]; /* now lets create the body of the post */ NSMutableData *body = [[NSMutableData data] autorelease]; NSString *str = [NSString stringWithFormat:@"Content-Disposition: form-data; name=\"userfile\"; filename=\"ipodfile%d.jpg\"\r\n",i]; [body appendData:[[NSString stringWithFormat:@"\r\n--%@\r\n",boundary] dataUsingEncoding:NSUTF8StringEncoding]]; [body appendData:[[NSString stringWithString:str] dataUsingEncoding:NSUTF8StringEncoding]]; [body appendData:[[NSString stringWithString:@"Content-Type: application/octet-stream\r\n\r\n"] dataUsingEncoding:NSUTF8StringEncoding]]; NSData *imageData = UIImageJPEGRepresentation([imgArray objectAtIndex:i], 90); [body appendData:[NSData dataWithData:imageData]]; [body appendData:[[NSString stringWithFormat:@"\r\n--%@--\r\n",boundary] dataUsingEncoding:NSUTF8StringEncoding]]; // setting the body of the post to the reqeust [request setHTTPBody:body]; // now lets make the connection to the web [NSURLConnection sendSynchronousRequest:request returningResponse:nil error:nil]; //NSString *returnString = [[NSString alloc] initWithData:returnData encoding:NSUTF8StringEncoding]; //NSLog(@"%@",returnString); [imageData release]; [request release]; //[body release]; } } It successfully upload the images to the folder and there is no any error in the execution but when it complete it process and try to go back it give error -[NSConcreteMutableData release]: message sent to deallocated instance Please help me out. Thanks