Treatment of disseminated low grade non-Hodgkin's lymphomas (NHL) remains unsolved. Despite an initial high remission rate (50%-70%) with chemotherapy, relapses occur and only 20 to 40% of patients are expected to be free of disease after 10 years. From 1981 to 1984, 113 low grade NHL were studied in order to determine factors influencing survival without progression. In a randomized trial, patients received either PCOP combination or PACOP for 6 months followed by chlorambucil or CVP for 12 months. Histological distribution was: follicular small cleaved cells 70 patients, follicular mixed 31 patients, small cells CLL type 12 patients. Stage distribution was: stage IV 88 patients with 74 bone marrow involvement, stage III 17 patients, stage II with bulky masses 8 patients. Complete response (CR) was observed in 49 patients at the end of treatment. Among the ten variables studied, only stage and the number of sites involved had a significant effect on the probability of achieving CR. Only CR significantly affected the freedom from progression (P less than 0.01). Median survival after progression was 21 months. Recently, alpha recombinant interferon has been proposed as treatment for low grade NHL. Cumulative results from the literature give a response rate of 42% on 139 patients. The response rate was higher in follicular NHL than in the CLL type, and response did not clearly correlate with dose. The CR rate was low (less than 20%) and relapses occurred after stopping therapy. Combined use of interferon and chemotherapy is proposed for future clinical trials.