Based on a preliminary trial that suggested that CHOP (cyclophosphamide, doxorubicin, vincristine, prednisone), and PVB (cisplatinum, vinblastine, bleomycin), are at least partially non-cross-resistant, the Southwest Oncology Group treated patients with unfavorable histology, non-Hodgkin's lymphoma with CHOP and PVB. In the first study, 76 eligible patients were given three courses of CHOP, with complete or partial responders receiving three courses of PVB followed by three further courses of CHOP. Nonresponders after the initial three cycles of CHOP, received six courses of PVB. In the second study, 154 eligible patients were treated with alternating cycles of the two drug regimens. The overall objective antitumor response (CR + PR) was 77% for the first study and 58% for the second. The complete remission rates were 48% and 38%, respectively. The overall survival for both studies is similar. These results are interpreted in terms of the Goldie-Coldman hypothesis.