Isotretinoin, an oral vitamin A derivative, is highly effective in, and at present indicated only for, the treatment of cystic acne, conglobate acne, or severe acne which has failed to respond to conventional therapy, including systemic antibiotics. Isotretinoin use usually results in a prolonged remission, often with complete disappearance of previously resistant lesions. Virtually all patients experience reversible integumentary side effects, which can almost always be controlled with emollients or lubricants. Isotretinoin is a known teratogen. The longterm effects of the transient vitamin A imbalance produced by this medication are not yet known.