From October 1984 to December 1989, 59 patients with aggressive non-Hodgkin's lymphomas (diffuse mixed, diffuse large cell, and immunoblastic) were treated with MACOP-B. All patients were previously untreated and most of them had advanced disease. Complete response (CR) was observed in 66%. Actuarial overall survival, failure-free survival (FFS), and relapse-free survival at 8 years were 54%, 52%, and 81%, respectively, with a median follow-up of 76 months (range: 28-92 months). The presence of B symptoms influenced significantly the CR rate, while FFS was affected by B symptoms, bone marrow involvement, and number of extranodal sites. Toxicity was high, with mucositis grade 2 or 3 occurring in 70%, leukopenia grades 3 or 4 in 80%, and death in 11.8% of the patients. MACOP-B was active in the treatment of aggressive non-Hodgkin's lymphomas, mainly in patients with few poor-prognosis factors, but other less toxic regimens would be more appropriate for this population. For poor-prognosis patients, new therapeutic modalities are necessary.