A phase II study was undertaken to assess whether continuous infusion of high-dose recombinant interleukin-2 (rIL-2) alone was active against different histologic subtypes of heavily pretreated lymphoma. Sixty one lymphomas were included in the study. rIL-2 (Roussel UCLAF, Romainville, France) was administered by continuous infusion at 20 x 10(6) IU/m2 for three cycles of 5 days, 4 days, and 3 days, during the first week, third week, and fifth week, respectively. Twenty-four low- grade non-Hodgkin's lymphomas (NHL) were resistant to an anthracycline- containing regimen. Twenty-three intermediate and high-grade NHL were refractory to initial treatment or to salvage therapy. Seven Hodgkin's diseases were refractory to at least three regimens or relapsed after autologous bone marrow transplantation. Seven mycosis fungoides were refractory to chemotherapy. In low-grade NHL, one complete response (CR) was observed. In aggressive NHL, there were three CRs and two partial responses (PRs). No response was noted in Hodgkin's disease. One CR and four PRs were observed in mycosis fungoides. Complete response durations were 23, 20, 17, 12, and 4 months. Grade 4 toxicity was observed in 29 patients leading to arrest of therapy in 12 patients. The response to rIL-2 therapy in lymphoma differs according to histologic subtypes. Five responses were observed in 23 aggressive lymphomas. Five of seven mycosis fungoides responded; these preliminary results warrant testing of a larger number of patients.