Retinoids, both naturally occurring and synthetic, are analogues of vitamin A. They represent a major advance in the treatment of acne and psoriasis, as well as rarer conditions such as the ichthyoses. The more frequent and widespread use of these drugs requires that the dermatologist be aware of the wide spectrum of adverse events that may be encountered with their use. Some are serious and irreversible, such as teratogenicity, necessitating great care if these drugs are given to women of childbearing potential. Other effects may be less severe, dose dependent and reversible. Although not devastating to the patient, appropriate advice may reduce morbidity.