In this double-blind, multicenter study, bupropion XL, a norepinephrine-dopamine reuptake inhibitor, and venlafaxine XR, a serotonin-norepinephrine reuptake inhibitor, were compared with regard to sexual functioning, efficacy, and tolerability. A total of 348 sexually active adult outpatients with depression were randomized to receive bupropion XL (titrated to a target dose of 300-450 mg/d) or venlafaxine XR (titrated to a target dose of 150-225 mg/d) for 12 weeks. Total scores on the primary dependent variable, the Changes in Sexual Functioning Questionnaire (self-report), increased for subjects receiving bupropion XL and decreased for those treated with venlafaxine XR; the mean change scores differed significantly between groups from week 2 onward. Among subjects with normal pretreatment sexual functioning, Changes in Sexual Functioning Questionnaire total scores remained essentially unchanged for the bupropion XL group but were decreased significantly for the venlafaxine XR group; mean change scores also differed between groups from week 2 onward. Although the therapies resulted in similar change on the 17-item Hamilton Depression Rating Scale, remission rates were significantly higher among those treated with bupropion XL (46%) versus venlafaxine XR (33%) (odds ratio, 1.93; 95% confidence interval, 1.07-3.46). Aside from adverse effects of venlafaxine XR on sexual function, both treatments were reasonably well tolerated. In conclusion, in this patient population (ie, relatively young, sexually active outpatients), bupropion XL was at least as effective as venlafaxine XR and had a significantly more favorable sexual side effect profile.