thanks " What you'll want to do is just to invalidate an area slightly larger than your rectangle.." I came to the same conclusion, but its just a bit nasty for my liking! I cant remember ever encountering this problem before, which is strange. it makes no sense at all why this occurs. Surely nothing should be displayed in an area that hasnt been invalidated. Why is this 1 pixel wide artifact occuring? Is this a bug with GDI+? --------------------------- Chris.