Kaposi's sarcoma is a malignancy for which there is no satisfactory standardized, nor even a very good, method of treatment. When the condition is indolent and but slowly progressive on the feet, where it is most common, conservative measures of good local hygiene and palliation of edema, if present, by mechanical support of circulation by elastic garments is generally advised. Small, dispersed nodules on the feet or hands, if symptomatic or subject to trauma, are amenable to extirpation by minor surgical procedures. When, however, the disease becomes continuous, symptomatic, extensive, or rapidly progressive and threatens to become disabling, radiotherapy is a first and best treatment. Helpful as radiotherapy may be in such cases, it is not and cannot be expected to be curative because it is practiced only on limited areas of clinically evident process and in that way does not influence the unpredictable rate of progression nor prevents development of multicentric foci of the disease in its capricious course. It is suggested that widespread radiotherapy in conservative doses be accorded early and prophylactically in cases of Kaposi's sarcoma immediately upon diagnosis and surely upon threat of rapid progression. There is precedent for such treatment in the extensive radiation practiced in Hodgkin's disease. Such treatment may prevent or at least halt progression of Kaposi's sarcoma by affecting clinically undetectable, active foci and foci in potential of malignant transformation. It can be designed to do no harm.