Kaposi's sarcoma of the genitalia is an infrequent complication of the acquired immunodeficiency syndrome but it often is difficult to manage. A total of 19 men (mean age 39 years) with penile and/or scrotal lesions underwent radiotherapy at dosages of 600 to 3,000 cGy. in fractions of 150 to 800 cGy. Of the patients 6 achieved a complete and 10 a partial response, while 2 had no response and 1 died too soon after treatment to be evaluated. Recurrences were noted in 8 patients, 7 of whom received additional radiation (1 patient had 2 recurrences and both responded). Of the retreatments 3 effected complete and 4 partial responses. Over-all, of 25 evaluable treatment courses 9 complete (36%) and 14 partial (56%) responses yielded a total response rate of 92%. There was 1 complication, a skin ulceration. Radiation therapy is well tolerated and will result in effective palliation in the majority of patients with Kaposi's sarcoma of the genitalia.