Between June 1986 and December 1988, we treated 149 patients who had AIDS-related epidemic Kaposi's sarcoma with cutaneous irradiation. According to Mitsayasu's staging, 34 patients (23%) had Stage I disease, 82 (55%) Stage II, 0 Stage III, and 33 (22%) Stage IV. Fifty-eight patients (39%) had previously presented with one or more opportunistic infections. Ninety-four patients (63%) had received previous treatment of their Kaposi's sarcoma: 85 (57%) with interferon and 43 (29%) with vinblastine. Among the 149 patients, we treated 88 (59%) with extended cutaneous irradiation using 4- and/or 8-MeV electron beam energy and 61 patients (41%) with localized irradiation using 45-kVp x-ray energy. The total prescribed dose was 30 Gy: 20 Gy in 2 weeks (2.5 Gy/fraction, 4 times/week), followed by 2 weeks of no irradiation, and then 10 Gy in one week by the same dose schedule. Twenty patients (13%) with edema of the lower limbs were treated using 4-Mv photon therapy with bolus. Of the 131 evaluable patients, 63% achieved a complete remission (CR) and 30% a partial remission (PR) after a mean period of 1.5 months (range: 0.5-3 months). The clinical disease stage, anatomic site, and irradiation technique did not significantly influence the remission rates, although we noticed a higher CR rate when localized irradiation was used (71% vs 55.5% for localized and extended irradiation, respectively; p = 0.08). The overall tolerance was acceptable. Complications were severe epidermitis with skin ulcerations (8% of patients), exudative epidermitis (26%), dry epidermitis (60%), and varying degrees of erythema (6%). Of the 87 patients whose AIDS remained relatively clinically stable during the observation period, recurrences occurred in 56 (64%) after an average of 5.5 months (range: 1.5-12 months). We conclude that radiotherapy is useful and can be recommended as a palliative treatment to relieve pain and physical discomfort or to achieve cosmetic improvements for patients with epidemic Kaposi's sarcoma. We also conclude that radiotherapy is most beneficial in the early stages of disease, when localized treatment is practical.