The efficacy and safety of adapalene 0.1% gel in the treatment of acne vulgaris has been demonstrated in multiple controlled clinical trials. A higher concentration formulation, adapalene 0.3% gel, has been developed to provide a broader range of treatment options for acne management. Phase 3 clinical studies have demonstrated the superior efficacy of adapalene 0.3% gel compared to adapalene 0.1% gel and its vehicle at the end of a 12-week treatment period. The goal of this study was to evaluate the long-term safety of adapalene 0.3% gel in subjects treated once daily for 52 weeks, with a secondary objective to evaluate long-term efficacy. Subjects 12 years of age or older (N=551) with acne vulgaris participated in a multicenter, open-label study of the long-term (up to 52 weeks) efficacy and safety of once-daily applications of adapalene 0.3% gel. Of those enrolled, 167 subjects completed 12 months of treatment. Expected signs and symptoms of local cutaneous irritation (erythema, dryness, scaling, and stinging/burning) were mostly mild or moderate, with mean tolerability scores below 1 (mild) at all time points for the parameters assessed. Treatment-related, dermatologic adverse events were experienced by 21% of subjects and dry skin, skin discomfort, and scaling were reported by 10.5%, 8.3% and 3.3% of subjects, respectively. Most of the adverse events reported occurred in the first quarter of treatment. Adverse events were mostly mild to moderate in severity. Subjects treated with adapalene 0.3% gel for 52 weeks achieved a >75% median reduction in total, inflammatory, and noninflammatory lesions in this open-label study by the end of the treatment period. Adapalene 0.3% gel was safe and effective in the long-term (up to 1 year) treatment of subjects with acne vulgaris.