Oral retinoids are now well-established drugs for the systemic treatment of skin diseases. For etretinate to be effective on a long-term basis it is recommended that maintenance therapy should be continued for 3-6 months after clinical signs of the disease have disappeared. In "non-responders" with psoriasis the blood levels of etretinate may be low and increasing the dose to 1.5 mg/kg body weight per day will be necessary and helpful in some cases. The interaction of drugs should also be considered carefully in non-responding individuals. Children usually respond well to treatment, but they also often require higher dose levels. Bone toxicity with premature epiphyseal closure and hyperostoses may be seen during isotretinoin administration and, more rarely, in patients receiving etretinate, but the risk is relatively low. Teratogenicity is a major concern in young females being treated for acne with isotretinoin, since 70 embryopathies have been recorded worldwide.