Perhaps better (adds '.png' more easily, keeps original case): ... for name in files: lname = name.lower() # if on windows for ext, names in filenames.iteritems(): if lname.endswith(ext) and 'ocean' in name: names.append(os.path.join(root, name)) self.listbox1.insert(END, name) break ... -- -Scott David Daniels Scott.Daniels at Acm.Org