Clonazepam and placebo were administered in a double-blind pilot study to 75 outpatients with social phobia. The mean maximum dose of clonazepam was 2.4 mg/day at endpoint (range, 0.5 to 3 mg). Treatment was continued for up to 10 weeks. The results of an intent-to-treat analysis indicated superior effects of clonazepam on most measures. Response rates for clonazepam and placebo were 78.3 and 20.0%. Drug effects were apparent on performance and generalized social anxiety, on fear and phobic avoidance, on interpersonal sensitivity, on fears of negative evaluation, and on disability measures. Significant differences were evident by week 1, 2, or 6, depending upon the rating scale used. Clonazepam was well tolerated in general, although unsteadiness and dizziness were more severe and persistent than was the case for placebo subjects.