Initial results from studies with third-generation combination chemotherapy regimens for the treatment of aggressive non-Hodgkin's lymphomas (NHL) demonstrated complete remission (CR) rates higher than those reported with first-generation regimens. Long-term follow-up of these studies is required to know if the increased number of CRs translates into an increased number of long-term disease-free survivors. In this report, results obtained with one of the third-generation regimens, ProMACE (prednisone/methotrexate/doxorubicin/cyclophosphamide/etoposide)-Cyta BOM (cytarabine/bleomycin/vincristine/methotrexate) are described. From 1981 to 1988, 193 patients with stage II, III, or IV aggressive NHL treated at the National Cancer Institute were randomly assigned to receive either ProMACE (day 1)-CytaBOM (day 8) or ProMACE (day 1)-MOPP (mechlorethamine/vincristine/procarbazine/prednisone) (day 8). With a median follow-up of 5 years, the CR rate was 86% for ProMACE-CytaBOM v 74% for ProMACE-MOPP (P = 0.048). A plateau in the disease-free survival curve is seen at 69% for ProMACE-CytaBOM v 54% for ProMACE-MOPP (P = 0.082). A plateau is also seen in the overall survival curves at 69% for ProMACE-CytaBOM v 53% for ProMACE-MOPP (P = 0.046). The Southwest Oncology Group also conducted a phase II study of ProMACE-CytaBOM in 78 patients with stages II to IV intermediate- or high-grade NHL to determine the CR rate and long-term disease-free survival of this regimen in a national cooperative group setting. The CR rate was 65%. With a median follow-up of 38 months, disease-free survival is 50% at 3 years and overall survival is 57% at the same time point.(ABSTRACT TRUNCATED AT 250 WORDS)