Previous studies have established CHOP (cyclophosphamide, doxorubicin, vincristine, prednisone) as the standard of comparison for treatment programs for patients with advanced stages of aggressive non-Hodgkin's lymphomas. Three sequential CHOP studies conducted by the Southwest Oncology Group (SWOG) showed a complete remission (CR) rate of 53% for 418 patients. This rate did not vary among the three studies. Median age was over 55 years. Relapse-free survival of CRs plateaued at 4 to 5 years. Approximately 21% of all patients in the first study and 33% of all patients in the following two studies are long-term survivors and presumed cured. Survival was clearly a function of patient age. Approximately 45% of all patients under age 55 at the time of treatment are cured by CHOP chemotherapy. To determine the toxicity, CR rate, and patient survival of m-BACOD (methotrexate, bleomycin, doxorubicin, cyclophosphamide, vincristine, dexamethasone), ProMACE-CytaBOM (prednisone, methotrexate, doxorubicin, cyclophosphamide, etoposide, cytarabine, bleomycin, vincristine, methotrexate), and MACOP-B (methotrexate, doxorubicin, cyclophosphamide, vincristine, prednisone, bleomycin), SWOG initiated a series of phase II studies. Of 118 eligible patients in the m-BACOD study, the median age of 85 patients treated with the full-dose regimen was 54 years, while the median age of 33 patients who started therapy at reduced doses was 67 years. Fatal toxicity was observed in 6% of patients receiving full doses and 13% of those receiving reduced doses. Life-threatening toxicity occurred in 31% of patients on the full-dose regimen and 34% on the reduced-dose regimen. CR was 65% for full-dose treatment, but 27% for reduced doses.(ABSTRACT TRUNCATED AT 250 WORDS)