The efficacy and safety of fluvoxamine maleate, a selective serotonin reuptake inhibitor, was compared with placebo and imipramine in patients with major depressive disorder. Previous literature has cited a dose range of 100 to 300 mg/day of fluvoxamine maleate for the treatment of major depression; however, this study demonstrates that a dose range of 50 to 150 mg/day is as effective as imipramine (80-240 mg/day). After a 1- to 2-week, single-blind, placebo washout phase, 150 depressed outpatients were randomized to double-blind treatment with fluvoxamine maleate (50-150 mg/day), imipramine (80-240 mg/day), or placebo for 6 weeks. Fluvoxamine produced a significant therapeutic benefit over placebo (p < or = 0.05) as assessed by the total score on the Hamilton Rating Scale for Depression; imipramine (80-240 mg/day) produced similar results. The secondary outcome variables (i.e., Clinical Global Impression severity of illness item and 56-Item Hopkins Symptom Checklist depression factor) also showed significant differences between fluvoxamine maleate and placebo during three of the four final weeks of the study. Both fluvoxamine maleate and imipramine appeared to be safe and well tolerated by the majority of patients. As expected from the pharmacology of these agents, the imipramine groups reported more anticholinergic effects (dry mouth, dizziness, and urinary retention) and electrocardiographic effects, whereas the fluvoxamine group reported more nausea, somnolence, and abnormal ejaculation. The majority of these adverse events were mild to moderate and, with the exception of dry mouth (imipramine) and abnormal ejaculation (fluvoxamine), were transient. The data clearly demonstrate the antidepressant activity and tolerability of fluvoxamine maleate (50-150 mg/day) as compared with placebo; it is also as effective as the tricyclic antidepressant imipramine (80-240 mg/day) in patients with major depressive disorder.