Thirty patients with recurrent suppurative hidradenitis entered a double blind trial to evaluate the effect of topical clindamycin against placebo in hidradenitis. Twenty seven patients concluded the 3 months' treatment. The overall effect of clindamycin treatment based on patients' assessments, number of abscesses, inflammatory nodules and pustules was significantly better than placebo at each monthly evaluation (P less than 0.01). When each parameter was evaluated separately, clindamycin was significantly superior to placebo except for inflammatory nodules and abscesses on the second and third months' evaluation. No side effects were recorded and the treatment was easy to administer. Topical clindamycin may be helpful prior to radical surgery or spontaneous remission.