Thank you very much! That's all that was needed. James Logajan <JamesL at Lugoj.Com> wrote in message news:<3B44F685.4F00FA2 at Lugoj.Com>... > You are missing a line. Before root.mainloop(), add the line: > > x = fibon_gui(root) > > Otherwise you aren't creating any instance of class fibon_gui that I can > see!