Seventy-one patients with advanced stage diffuse large cell lymphoma were treated with MACOP-B. Sixty-nine per cent of patients achieved a complete response (CR), 10% a partial remission, while 11% had no response and 10% died because of toxicity. The CR rate was adversely affected by immunoblastic type, poor performance status and bone marrow involvement. Two-year survival for all 71 patients was 55% and 2-year disease-free survival (DFS) for the 49 CRs was 73%. Relapses were lower (P less than 0.05) in patients achieving CR in 8 weeks or less (DFS 83% vs. 59%) and in patients without tumor bulk (DFS 87% vs. 54%). Overall toxicity was acceptable with mucositis proving to be the most frequent severe side-effect. However, treatment-related deaths were unacceptably high in patients over 59 years of age (30% vs. 7%). Thus for the elderly MACOP-B is potentially lethal and must be used cautiously. These preliminary results confirm the effectiveness of MACOP-B. The delay of response and/or the presence of tumor bulk may be important prognostic factors in identifying a subset of poor risk patients with a high incidence of relapse.