Twenty patients with stage III and IV diffuse well-differentiated lymphocytic lymphoma were treated with combination chemotherapy consisting of BCNU, cyclophosphamide, vincristine, melphalan and prednisone (M-2). Treatment was given every 5 weeks for 11 cycles in responding patients. The median age of the patients was 62 years (range 45-76). There were 12 complete remissions and 6 partial remissions for an overall response rate of 90%. The median duration of remission was 24 months (range 12-79 months) and was identical for complete responders and partial responders. All but 2 responding patients have been subsequently retreated for relapse. The median survival was 84 months (range 1-108 months). Myelosuppression was mild. Nausea/vomiting, neuropathy, alopecia and gastrointestinal symptoms from prednisone were seen in the minority of patients. One patient expired from sepsis/neutropenia during the first cycle of therapy. The M-2 protocol produces effective remissions in diffuse well-differentiated lymphocytic lymphoma. The relapse and survival pattern are similar to the results achieved with other chemotherapy regimens in low-grade lymphoma.