A 24-week, double-blind, randomized trial was performed to compare the efficacy and tolerability of venlafaxine and paroxetine in patients with major depression or dysthymia. Outpatients aged 18-70 years with a baseline score of 17 on the 21-item Hamilton Depression Rating Scale (HAM-D) were eligible. Patients were randomly assigned to venlafaxine, 37.5 mg, in the morning and evening or paroxetine, 20 mg, in the morning and placebo in the evening, which could be increased to venlafaxine, 75 mg twice daily, or paroxetine, 20 mg twice daily, after 4 weeks. Efficacy was assessed with the 21-item HAM-D, the Montgomery-Asberg Rating Scale, the Hamilton Anxiety Rating Scale, and the Clinical Global Impressions Scale. Forty-one patients were randomized to venlafaxine and 43 to paroxetine. At week 6, a response was observed in 55% of patients on venlafaxine and 29% on paroxetine (P = 0.03). At week 12, significantly (P = 0.011) more patients in the venlafaxine group had a HAM-D remission score of 8 or less (59% versus 31%). Discontinuation for any reason occurred in 16 (39%) patients on venlafaxine and 11 (26%) on paroxetine. The most common adverse events were nausea (28%), headache (18%) and dry mouth (15%) with venlafaxine and headache (40%) and constipation (16%) with paroxetine. Venlafaxine was effective and well tolerated for the treatment of patients with mild to moderate depression or dysthymia. A consistently higher proportion of patients had a response or remission on venlafaxine than on paroxetine.