In a double-blind clinical study in ninety-four subjects a 1.5% (w/v) erythromycin lotion was as effective as 5% (w/v) benzoyl peroxide gel in significantly reducing the number of small inflamed lesions and the overall acne severity. However, benzoyl peroxide also significantly reduced the number of non-inflamed lesions whereas erythromycin had no effect on these lesions. This study supports the view that, although topical erythromycin is of value in the treatment of mild or moderate acne vulgaris, long established, safe and effective remedies should not be replaced by topical antibiotics until more comparative studies and investigations on bacterial resistance have been completed.