In addition to the Control.InvokeRequired property, there are four methods on a control that are thread safe: Control.Invoke(Delegate), Control.BeginInvoke(Delegate), Control.EndInvoke(IAsyncResult), and Control.CreateGraphics if the handle for the control has already been created. Calling Control.CreateGraphics before the control's handle has been created on a background thread can cause illegal cross thread calls. For all other method calls, you should use one of the invoke methods to marshal the call to the control's thread.