The efficacy and safety of topical 1.5% erythromycin solution and 1% clindamycin phosphate solution were compared in the treatment of acne. The number of inflammatory lesions was significantly reduced at 12 weeks by 62% and 59% and the number of noninflammatory lesions by 43% and 39% in the erythromycin and clindamycin groups, respectively. The reduction in lesions was also reflected in the clinical evaluation of the overall facial condition; 73% of the 74 patients treated with erythromycin solution and 62% of the 80 patients treated with clindamycin solution had excellent or good responses at 12 weeks. The results of this study show that topically applied 1.5% erythromycin and 1.0% clindamycin solutions are both effective and comparable in reducing the clinical manifestation of acne in patients with moderate disease.