Sharon, is the screw into wood, metal or some other material? Is the screw missing its threads or does what the screw goes into have the hole too big now. It's generally possible to put a screw that is one size bigger in metal applications with drilling and tapping for a larger screw, or just replace the screw if that's whats bad. It's generally possible to put some more wood (toothpicks work well) into the hole and re-install the screw into wood. Knowing more about the problem would help us give you a better answer.