Human papillomavirus type 1-associated squamous cell carcinoma in a heart transplant recipient. The occurrence of squamous cell carcinomas in organ transplant recipients with warts represents a good model to study viral carcinogenesis. Most of the cases were reported in renal transplant recipients. We present the case of a heart transplant recipient in whom multiple common warts, preepitheliomatous keratoses, and squamous cell carcinomas developed. The warts began 4 years after the transplantation and the first carcinoma occurred 2 years after the warts, all the lesions being on sun-exposed areas. Histologic signs of human papillomavirus infection were seen in all premalignant and malignant lesions. Furthermore, human papillomavirus type 1 DNA was detected by in situ molecular hybridization within one of the carcinomas. Human papillomaviruses, along with other carcinogenic factors, play an important role in the development of carcinomas, and benign types could be implicated. Further studies are required to evaluate the frequency of cutaneous malignant neoplasms in heart transplant recipients as compared with renal transplant recipients. 