Warts and cutaneous squamous cell carcinomas are common complications of immunosuppression. We studied a total of 189 renal transplant recipients clinically for such lesions. The incidence of warts increased steadily after transplant, such that of patients transplanted for more than 5 years, 92% were found to have warts and 65% had more than five warts each. DNA extracted from scrapings of their warts showed they carried the same human papillomavirus types as the general population, and not the unique set found on patients with epidermodysplasia verruciformis (who share with transplant recipients an increased incidence of warts and squamous cell carcinomas).