Premenstrual syndrome is an extremely common disorder. Prospective documentation of symptoms and their temporal relationship to menstruation establishes the diagnosis of PMS. Because the pathophysiologic mechanisms causing PMS are still undetermined, therapy for PMS is largely empiric. A number of pharmacologic agents may be used to reduce PMS symptomatology, and therapeutic decisions should be tailored to the individual's symptom complex. Many women will be able to lead more productive lives if PMS is properly diagnosed and intelligently treated.