Four patients with extensive, unresectable desmoid tumors were treated with definitive radiation therapy. Three are free of disease 2 years after treatment; the tumor of the fourth has decreased to 20 per cent its former size 1 year after therapy by irradiation. The authors feel that surgery is the treatment of choice in cases of small lesions, but radiation therapy should be attempted in the more extensive tumors. Radical amputation should be reserved for only those patients in whom desmoid tumors failed to respond to radiation treatment.