In a placebo-controlled, double-blind study of 91 out-patient depressives, the anti-depressant effect of fluvoxamine, a selective serotonin uptake inhibitor was compared to that of imipramine. Overall drug effects were relatively weak but analyses in selected sub-groups showed both active drugs superior to placebo. Effects of fluvoxamine were more marked in non-situational depressives and it did not improve sleep while effects of imipramine were more marked in retarded depressives and on retardation ratings, suggesting that fluvoxamine may have a different pattern of clinical effects. Side effects of Fluvoxamine were predominantly gastrointestinal and it did not produce postural hypotension or anticholinergic side-effects.