A total of 31 patients with prostatic adenocarcinoma received a total of 35 half-body irradiation treatments; 13 treatments of 600 to 800 cGy. to the upper half and 22 treatments of 400 to 1,000 cGy. to the lower half of the body. The interval from the discovery of osseous metastases to symptomatic need for half-body irradiation was similar for all tumor grades and stages except for patients with well differentiated lesions, in whom this interval was significantly longer as was survival time after half-body therapy. Treatment was well tolerated and relief of pain was substantial. The majority of the patients obtained subjective relief evidenced by decreased use of narcotic analgesics or change to nonprescription medication. Median survival after half-body irradiation was 5 months. Palliative effects were maintained until death in 82 per cent of the patients treated to the upper and 67 per cent treated to the lower half of the body.