From January 1987 to December 1992, 420 patients with acquired immunodeficiency syndrome (AIDS)-related epidemic Kaposi's sarcoma (EKS) were treated with radiotherapy at the oncology department in the Henri Mondor Hospital. Of these, 146 (34.7%) exhibited tumours at 186 sites; 35 were oral, 102 eyelid or conjunctival (ophthalmic), and 49 penile or scrotal (genital) sites. Most patients had received prior chemotherapy. Radiation therapy consisted of 4 MV or 45 kV X-rays, depending on tumor size and location. Doses ranged from 10 to 30 Gy, according to tumor response and toxicity. In oral lesions mucosal reactions were often observed after relatively low doses of radiotherapy. In 27 patients receiving 15 Gy, severe reactions were observed in 6 (22%), moderate reactions in 4 (15%) and mild reactions in 17 (63%). By contrast, irradiation of eyelid or conjunctival lesions and genital lesions, was well-tolerated. Treatment was generally successful in achieving good symptom palliation. Eyelid and conjunctival Kaposi's sarcoma seemed to be more radiosensitive when compared with cutaneous sites: a high objective remission rate (96%, 98/102) was observed at doses ranging from 10 to 20 Gy. Penile and scrotal lesions showed a good response to low dose radiation (complete response was scored in 34/49 patients (69.4%)). A meticulous evaluation of tolerance was necessary. Toxicity of oropharyngeal irradiation at relatively low doses is an argument for a restrictive use of this procedure in oral lesions.