This multicentric pilot study was conducted in order to evaluate the feasibility of early interleukin-2 (IL2) after high dose chemotherapy requiring autologous bone marrow transplantation (ABMT). BCNU at 800 mg/m2 was followed, 3 days later, by the reinjection of the bone marrow cells. At day 4, IL2 at 18 x 10(6) i.u./m2/day was given as a continuous infusion during a minimum of 6 days (first phase of study) or for 6 more days after 1 day break (second phase of the study). Twenty patients were included. Toxicity was not negligible, with one toxic death, but IL2 therapy does not damage the haematological recovery of most patients. However, a 6-day IL2 treatment period only appears tolerable. In 18 evaluable patients, three responses were observed: one complete response (CR) of short duration in a non-Hodgkin's lymphoma, one CR (24 months +) and one partial response (PR) (6 months) in two patients with metastatic gastric adenocarcinoma. This study confirms that IL2, restricted to a 6-day treatment period, is feasible immediately after high-dose chemotherapy requiring ABMT without haematological problem in most patients. The response rate was unexpected for a pilot study and this combined therapy obviously requires further study.