Evidence is presented of an increasing incidence of skin tumours in a group of immunosuppresscd patients. Lesions seen were keratosis, keratoaeanthoma, Jiowen's disease, and carcinoma of the skin and of the; lip. Fourteen patients developed skin lesions in 151 patients receiving cadaveric renal transplants. The risk seemed to lie cumulative, with 28% of survivors 4 years or more after transplantation developing premalignant skin lesions and 17% developing skin cancers. Azathioprine and cyclophosphamide therapy were associated with similar skin lesions in nine patients not receiving transplants who were treated for renal and hepatic diseases.