A case of diffuse, epithelioid mesothelioma of the right pleura in a 16-year-old boy is presented. Though a history of previous exposure to asbestos could not be elicited, the patient did receive pulmonary irradiation for metastatic Wilms' tumor at the age of 2 years. The authors believe that the development of his mesothelioma was causally related to his prior radiotherapy.