• To examine the efficacy of the monoamine oxidase inhibitor phenelzine sulfate in the treatment of bulimia, a doubleblind, placebo-controlled trial was conducted. In 50 women who completed the trial, phenelzine was significantly superior to placebo in the reduction of binge frequency (64% vs 5%), in the fraction of patients who had ceased bingeing at the end of the trial (35% vs 4%), and in several measures of psychological state. The superiority of phenelzine over placebo was not confined to a depressed subgroup of patients. Although no patient experienced a hypertensive crisis during the study, other side effects of phenelzine were problematic and limit the usefulness of phenelzine in this population.