>Mark,
>Like Brian and George I didn't encounter it change at runtime. I have modules that hide the window, invoke other toplevel forms + track nonVFP apps, attaching to their thread input, detaching etc. I was scared from exactly the same phrase '... you cannot rely on its value ...' and used API to be sure. It wasn't changing. But I trust to doc writers until I can solidly tell the reverse:)
>For your case, while a form name is not unique you could make it unique at run time changing the form name :)

Yeah, I know I could change the form name at runtime, but that becomes a pain when I could just use an already built-in unique identifier. If it had turned out I could not rely on the hWnd, I would have resorted to just using SYS(3) or SYS(2015) to get a unique ID for the form.