BACKGROUND The effect of fluvoxamine versus placebo on serum cholesterol levels in obese women undergoing behavior therapy for weight reduction was evaluated. METHODS Forty obese female outpatients undergoing 13 weeks of a behaviorally oriented treatment program for weight reduction were randomly assigned to double-blind treatment with fluvoxamine 100 mg/day (N = 18) or placebo (N = 22). Total serum cholesterol levels were measured before and after the 13-week study period. RESULTS Patients of the two treatment groups did not differ in age, weight, body mass index, cholesterol levels before treatment, and the extent of weight reduction during treatment. Cholesterol levels were significantly lower after fluvoxamine treatment than before, whereas cholesterol levels remained unaltered after placebo administration. Patients with initially high total cholesterol levels (> or = 200 mg/dL) showed a significantly larger reduction than patients with desirable cholesterol levels. However, there was no interaction between treatment and initial cholesterol level. CONCLUSIONS The results might suggest a cholesterol-lowering effect of fluvoxamine.