Trouble Comparing String

I have a string that is set to a HTTP response. When I print the value to the console, it tells me it is -1. However, it is not working when I compare the string to @"-1". Is it possible that there is hidden information being encoded from the HTTP response?

Code:

NSData *returnData = [NSURLConnection sendSynchronousRequest:request returningResponse:nil error:nil];
	NSString *returnString = [[NSString alloc] initWithData:returnData encoding:NSUTF8StringEncoding];
	
	
	if([returnString isEqualToString:@"-1"]){
		NSLog(@"works");
			UIAlertView *alert = [[UIAlertView alloc] 
								  initWithTitle:nil message:@"That username is already in use." 
								  delegate:self cancelButtonTitle:@"OK" 
								  otherButtonTitles:nil]; 
		[alert show]; 
		[alert release]; 		
	}

 

Thanks for the help, I got it working by using if ([returnString rangeOfString"-"].location == 0).