Buspirone, a new nonbenzodiazepine anxiolytic agent, was compared with clorazepate in a double-blind, multicenter trial conducted with 336 outpatients who had moderate to severe anxiety. The two treatments were equally effective for relief of symptoms, including anxiety with associated depression. Although both agents were generally well tolerated, the profile of side effects was dissimilar. Drowsiness and depression occurred significantly (p less than 0.055) more frequently with clorazepate, whereas nausea and headache occurred significantly (p less than 0.055) more frequently with buspirone. Clorazepate-treated patients were significantly (p less than 0.055) more likely to have had an adverse experience that was considered drug related or that interfered with the therapeutic effect. In this study, buspirone was shown to be an effective antianxiety agent, causing significantly less sedation than clorazepate.