A follow-up was done on the patients of the German multicenter study with severe conglobate acne who had been treated with different dosages of 13-cis-retinoic acid. Eighty-seven patients were monitored from 12 to 21 months. Optimal long-term therapeutic effects were obtained with an initial dose of 1.0 mg/kg body weight, for 3 months, followed by another 3-month-treatment period with 0.2 mg/kg body weight. Six months after the termination of therapy 96% of the patients were still in remission and 81% after 12 months. Comparative figures for the administration of doses were 84% as opposed to 47% (0.5----0.2 mg/kg body wt.) and 74% as opposed to 37% (0.2----0.2 mg/kg body wt.), respectively. It is suggested from the present data that a high initial dosage of 13-cis-retinoic acid be chosen in order to obtain optimal long-term therapeutic effects. Transiently elevated lipid levels as well as other tolerable side effects return to normal within 3 months at the latest after discontinuation of treatment.