The combination of cyclophosphamide, adriamycin, vincristine, and prednisone (CHOP) alternating with total body irradiation (TBI) has been shown earlier to be effective therapy in patients with malignant lymphoma who have received prior chemotherapy and/or radiation therapy. A limited institutional pilot study was therefore done by the Southwest Oncology Group between October 1977, and November 1978 to test the benefit of this program in previously untreated persons with Stages 3 and 4 diffuse histology non-Hodgkin's lymphoma. Eleven evaluable patients with the following histologies were treated: 7 poorly differentiated, 2 with histiocytic, 1 with mixed lymphoma and 1 with well-differentiated morphology. CHOP was given in the following manner: cyclophosphamide 400 mg/M2 IV day 1, adriamycin 40 mg/M2 IV day 1, vincristine 2 mg IV day 1, and Prednisone 100 mg po daily X 5. Forty-five rad total body irradiation was delivered in three fractions on days 21, 23 and 25. Chemotherapy was repeated on day 42, etc., until four cycles of CHOP and three cycles TBI (135R) were delivered. Responses were seen in 8/11 patients (6 CR and 2 PR); 5 persons are currently alive and 6 are dead. Two of the living patients are alive with disease and the remainder are in unmaintained remission. Two persons died with no response and one died in complete remission of an unrelated illness. The median duration of remission is 15 months and the median survival for all patients is 48 months. The therapy was well tolerated with a mean nadir leukocyte count of 3,020 X 10(9)/microliters (range 1.2-5.5) and a mean nadir platelet count of 188 X 10(9)/microliters (range 016-270). As delivered, this program is capable of producing durable remissions and needs to be verified in a larger series of patients.