A single radiation fraction of 800 cGy was used in the treatment of acquired immunodeficiency syndrome (AIDS)-associated Kaposi's sarcoma (KS). A total of 74 radiation treatments was given to a total of 31 patients. Of all 74 evaluable treatments, there were 25 objective major responses (6 complete, 19 partial) according to the WHO criteria, while 67 treatments resulted in subjective palliation of the main reason to treat (cosmetic discomfort, pain, or oedema). However, it appeared that the duration of these responses was rather short; in 23 of 36 radiation treatments with a follow-up of more than 4 months, progression of the tumour was seen within that time, while the palliative effect outlasted the survival of the patients in only four cases. It is concluded that a single dose of 800 cGy is an effective treatment for patients with a predicted survival of only a few months, and it should be determined whether a higher fractionated dose improves duration of responses, especially for patients with a good performance.