Tetracycline, because of its effectiveness, safety, and economy, remains the treatment of choice for chronic maintenance of uncomplicated acne. However, a certain percentage of patients with very difficult acne will not respond satisfactorily to tetracycline. The study presented herein described forty-two patients with nodulocystic acne who did not show imporvement on adequate trials of tetracycline and were switched to low-dose clindamycin. A majority of these patients then showed significant improvement with nine showing essential clearing of the condition. Two patients experienced diarrhea, but recovered immediately after the clindamycin was discontinued.