Among the large variety of effects of acetylcysteine, several of them relate to cutaneous function in general and to sebaceous activity in particular. Due to the latter, a study was undertaken to investigate a possible effect of this substance in grade I acne. An analysis of the data from 99 patients in a double-blind study demonstrated that 5% acetylcysteine topical gel is significantly superior to placebo (P = .04) in reducing comedo counts. Comparable results were obtained in both sexes. This study indicates that acetylcysteine is an effective therapeutic option for the treatment of mild to moderate acne.