80 patients with previously untreated CLL have been admitted to the Radiation Oncology Branch of the NCI. Fourteen of these patients have remained classified as 'indolent' until the present time and have not received any treatment. 48 patients with 'active' CLL were treated with TBI and were compared with 18 patients treated with chemotherapy and/or local irradiation. Our series of patients primarily treated with TBI have twice the median survival (57 months) measured from first therapy of the concurrent chemotherapy series (27 months). One third of the TBI group have experienced a complete or nearly complete remission and these patients showed a definite longer survival, with a median survival well in excess of five years until now. However, patients with a less complete remission failed to demonstrate a prolonged survival time with TBI in comparison to other modes of treatment. These results indicate that TBI can induce complete remissions which improve the prognosis in patients with active CLL.