There is an increased incidence of Kaposi's sarcoma (KS) in organ transplant recipients in whom it comprises more than 3% of all de novo neoplasms. Any such patient who develops reddish blue macules or plaques in the skin or oropharyngeal mucosa, or has apparently infected granulomas that fail to heal, should be suspected of having KS. In 45% of the patients, the internal viscera are involved. This variety has a bad prognosis. Apart from conventional treatment with surgical excision, radiotherapy or chemotherapy, cessation, reduction, or modification of immunosuppressive therapy produces gratifying results in a significant number of patients.