In 42 patients with high-grade malignant non-Hodgkin lymphomas, a new treatment program was used in an attempt to improve results without increasing toxicity. Two effective but relatively well tolerated and non-cross resistant drug combinations were given sequentially according to the response of disease. Therapy was started with a combination consisting of cyclophosphamide, doxorubicin, bleomycin, vincristine, procarbazine and prednisone (CABOPP). In patients with complete remission after a maximum of 4 cycles of CABOPP, this regimen was continued for a total of 6 cycles. In patients with progressive disease or with only a partial remission after 4 cycles of CABOPP, therapy was switched to a combination consisting of etoposide, ifosfamide and methotrexate (VIM). Complete remission (CR) was achieved in 86% of patients. Sixty-nine percent achieved CR with CA-BOPP alone and 17% after changing to VIM. The CR rate was 100% in patients with stage I or II and 78% in those with stage III or IV of disease. The projected survival at 2 years is 66%. Fifty-six percent of patients with CR are predicted to have continued CR at 2 years. Thus, CABOPP/VIM appears to be an effective and well tolerated program for the treatment of aggressive lymphomas. The value of this program, however, can only be established comparing it with other newly developed protocols in randomized studies.