A major pathogenic factor of acne is the disturbed keratinization of the follicular infundibulum. It has been hypothesized that a relative decrease in linoleic acid in the sebum could be responsible, in part, for this. The aim of the present study was objectively to evaluate the effects of topically applied linoleic acid on the size of microcomedones in patients with mild acne. The design was a double-blind placebo-controlled randomized cross-over study. Evaluations were performed by digital image analysis of cyanoacrylate follicular biopsies. There was a significant effect of topically applied linoleic acid on the size of follicular casts and microcomedones, an almost 25% reduction in their overall size being achieved over a 1-month treatment period. In contrast, no change was found at placebo-treated sites. It is concluded that topical linoleic acid might play a role as a comedolytic agent in acne-prone patients.