Forty-eight patients with acne vulgaris in the face were treated with a water-based (Basiron) and an alcohol-based (Panoxyl) 5% benzoyl peroxide preparation. A randomized double-blind, contralateral study was used. No difference in clinical effect was found. Treatment for 8 weeks resulted in at least 50% reduction in the number of closed comedones, papules and pustules in over 80% of the patients. In more than 70% of the patients, the reduction exceeded 75%. The water-based Basiron caused significantly less skin irritation than the alcohol-based preparation of Panoxyl.