A 12-week, randomized, double-blind, vehicle-controlled study evaluated the efficacy and safety of once-daily adapalene 0.1%-benzoyl peroxide 2.5% (ADA-BPO), ADA 0.1%, BPO 2.5%, or vehicle in 1,670 patients with acne vulgaris (AV). The primary endpoint was the success rate (a rating of "clear" or "almost clear" on the Investigator's Global Assessment [IGA] scale) at 12 weeks. The success rate was 37.9, 21.8, 26.7 and 17.9% in ADA-BPO, ADA, BPO and vehicle groups, respectively (ADA-BPO vs. ADA; ADA-BPO vs. BPO; ADA-BPO vs. vehicle, all P < 0.001). Success rate increased significantly from week 2 and continued throughout week 12. Adverse events judged to be treatment-related were 31, 19, 13 and 8% in ADA-BPO, ...