We evaluated 1179 consecutive patients with low-grade B-NHL diagnosed according to criteria of the Kiel classification and presenting with initial bone marrow involvement. Therapeutic approaches were not changed during the observation period 1975-1995. CLL (n=895) and IC (n=169) were treated palliatively with chlorambucil/prednisone or prednimustine. In CBCC (n=65) and CC (n=50) remission was induced with COP or CHOP. The overall response rate was 67%, but only 35% of CBCC and 23% of CC patients achieved complete remission. Median survival was 64 months in CBCC and 28 months in CC. As the median age of our patient population was 68 years (range: 23-93) it seems doubtful whether overall prognosis can be improved by aggressive therapeutic measures. One exception might be CBCC patients who were younger (median age 56 years) and who were usually in good general condition so that they might qualify for high dosage chemotherapy and stem cell support. Whether the prognosis of IC and CLL (median survival 74 months and 107 months, respectively) can be improved by treatment with drugs such as purine analogs will depend on the long-term outcome of clinical studies.