Chemotherapy using cyclophosphamide, doxorubicin, etoposide, cytarabine, bleomycin, vincristine, methotrexate with leucovorin, and prednisone (ProMACE-CytoBOM) for patients with intermediate- and high-grade non-Hodgkin's lymphomas was tested by the Southwest Oncology Group (SWOG) to confirm the activity of the regimen and to test the feasibility and safety of administering third-generation drug regimens in a cooperative group setting. On day 1, cyclophosphamide, doxorubicin, and etoposide were administered, followed by cytarabine, bleomycin, vincristine and methotrexate with leucovorin given on day 8. There were 51 complete remissions (CRs) among 78 previously untreated patients (65%) having clinical stage II-IV disease. The median length of follow-up is 37.9 months with 57% of patients alive at 3 years and 50% of CR patients free of disease at 3 years. Patients with diffuse large-cell lymphoma have the best survival (63% at 3 years) and relapse-free survival (RFS; 68% at 3 years with no relapses seen after 14 months). Administration of ProMACE-CytoBOM is feasible and safe in a cooperative group setting with 84% of 537 courses of treatment given exactly according to schedule and fatal toxicities seen in five patients (6%). ProMACE-CytaBOM may represent improved treatment for diffuse large-cell lymphoma, but the modest differences compared with cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOP) indicate the need for a prospective randomized comparative trial.