One hundred and forty-one consecutive patients above and 231 below the age of 60 years with previously untreated intermediate or high grade non-Hodgkin's lymphoma were included in this study. Patients above the age of 60 years were treated with the COPP chemotherapy regimen. The younger patients, at or below the age of 60, received a doxorubicin-containing regimen (119 had CHOP, 65 had BACOP and 47 had m-BACOD). For stage I patients, the clinical results were similar but for stage II, III or IV disease, those receiving COPP had significantly worse CR rate and survival than those who had a doxorubicin-containing regimen. Multivariate analysis on patients receiving the COPP chemotherapy revealed that the independent prognostic variables significantly determining CR rate and survival included clinical stage (p = 0.04) and serum lactate dehydrogenase level (p = 0.001). Myelosuppression was the major toxicity following COPP chemotherapy in this group of patients. There were 10 (7 per cent) treatment-related deaths. Compared to the reported results using doxorubicin-containing regimens to treat elderly patients with aggressive NHL in the literature, the more aggressive treatment does not appear to improve significantly the clinical outcome of this group of patients and seems to produce treatment results very much similar to COPP. However, accurate comparison is difficult because of the variation in the patient characteristics. Further prospective controlled randomized trials will be necessary to determine the optimal therapy for these patients.