Efficacy and tolerability of a gel preparation with 0.025% tretinoin and 4% erythromycin in acne vulgaris was evaluated in an open multicentre study. A total of 1337 patients of either sex, aged 8 to 68 years, were enrolled in the study; 13 had to be excluded from analysis. Some 499 patients had received former acne treatment; this was described as non-efficient or poorly efficient in 90% of the patients. The treatment period lasted up to 14 weeks. Efficacy was determined by counting the acne lesions (comedones, papules and pustules) before drug administration and every second week during the treatment period. Lesions had diminished after 2 weeks in about 35% of the patients. At the end of the treatment period, comedones were eliminated in 47.0% and improved in another 41.4%. Papules were eliminated and improved in 58.2% and 32.6%, pustules in 74.3% and 18.3% respectively. Side-effects (erythema, burning, pruritus, scaling and dryness of the skin) occurred in 203 patients (15.3%). Treatment was stopped in 25 subjects (1.9%) due to intolerance reactions. The results of the present study thus confirm the high efficacy and tolerability of the fixed combination observed previously in more selected patients. The fixed combination of tretinoin and erythromycin makes retinoic acid treatment possible even by a general practitioner.