Twenty-two patients with non-Hodgkin's lymphoma (NHL) were treated with a combined regimen of interferon alfa-2b (Intron A; Schering-Plough) and chlorambucil to evaluate the response and efficacy in pre-treated or relapsed patients. Ten patients were classified as having follicular lymphoma and 12 diffuse lymphoma. The treatment schedule consisted of interferon alfa-2b 3 X 10(6) IU/m2 thrice-weekly and chlorambucil 10 mg daily for three weeks, with a week's rest between each cycle. Treatment continued for upto six cycles. We obtained two complete remissions (CR), 12 good partial remissions (GPR), seven no remissions (NR) and one stable disease. On histologic examination we observed a response in 8 of 10 patients with follicular lymphoma (2 CR and 6 GPR); three of five patients with diffuse mixed lymphoma, and three of seven patients with diffuse lymphoma showed GPR. The major toxicity consisted of fever and nausea and, in one case, lethargy. In one patient the treatment was stopped at the second cycle because of poor compliance. Hematologic toxicity was generally mild and occurred between the third and fourth cycle. We observed hepatic toxicity i.e. a transient increase of transaminase levels, in three patients. We consider this regimen to be effective in the treatment of relapsed or resistant NHL and no more toxic than single agent therapy. A randomized study to verify this therapeutic approach versus conventional therapy with chlorambucil alone in first-line treatment is recommended.