Obsessive-compulsive disorder is a well-defined clinical syndrome which is difficult to treat. The author details various medical & psychological therapies. He states there is a “hidden epidemic” of silent sufferers who will begin seeking treatment as the efficacy of serotonin anti-depressants & behavioral therapy become more widespread. He concludes that the serotonin model raises the question of whether a commonality in the biology of compulsions, impulsivity, bulimia, & suicide exists. (VM)