This series of studies was undertaken to assess the safety profile of sustained-release (SR) bupropion in the treatment of depressed outpatients. Adults with a diagnosis of major depression were evaluated in 1 of 3 multicenter, randomized, double-masked, parallel-group, placebo-controlled trials conducted in private-practice psychiatric outpatient clinics. Following a 1-week, single-masked, placebo lead-in period, patients received bupropion SR for 8 weeks (study 1: 150 or 300 mg/d; study 2: 100, 200, 300, or 400 mg/d; study 3: 50 to 150 or 100 to 300 mg/d). Safety assessments included monitoring adverse events, patient discontinuation rates, changes in weight, vital signs, and clinical laboratory test results. Across studies, the most frequently reported adverse events were headache, dry mouth, and nausea. The incidence of adverse events was similar (< or =5% difference) between the bupropion SR and placebo groups, with the exception of dry mouth (bupropion SR, 16%; placebo, 7%). Dry mouth, nausea, and insomnia occurred significantly more often in bupropion SR-treated patients than in patients who received placebo (P<0.05). Nearly all (94% to 99%) adverse events reported in these studies were mild or moderate. Less than 10% of patients in either group discontinued treatment prematurely because of adverse events, and no deaths or serious drug-related adverse events were reported. Sexual dysfunction was reported as an adverse event by <1% of patients in either group. Bupropion SR was associated with dose-related weight loss in all 3 studies. No consistent patterns of change were observed in vital signs or in the results of clinical laboratory tests. Data from these 3 clinical trials demonstrate the favorable safety profile of bupropion SR in the treatment of depressed outpatients.