Low grade malignant follicular lymphoma is characterized by its slow course over many years. However, despite a median survival of 4 to 8 years the cure rate is lower than 10 percent and even nil for some authors. The best therapeutic approach of the disease is unknown, and many teams of oncologists are in favour of a more intense chemotherapy. We present a study of 10 patients selected for their young age and for the presence of detrimental prognostic factors (index 3 of Coiffier's classification in 8/10 patients). Nine patients received BCNU, cytosine arabinoside, etoposide and melphalan, followed by reinjection of autologous bone marrow purged in vitro by mafosfamide in the adjusted dose CFUGM LD 95. Eight of these 9 patients are in complete, unmaintained remission 15 to 43 months after the bone marrow transplantation (including 3 patients in a more than 2 years' remission). The 10th patient had autologous bone marrow transplantation in 1979; after treatment with heavy TACC chemotherapy followed by reinjection of unpurged bone marrow, he remained in complete remission for 9 years, then relapsed; he is now alive with a progressive tumour. Although the follow-up was relatively short for a particularly slow disease, this study shows that, owing to autologous bone marrow transplantation as early as the first complete remission, one of the heaviest types of chemotherapy can be delivered in patients with non-Hodgkin's lymphoma, unless precluded by toxicity. At the moment, this protocol is experimental and can be used only in young subjects at high risk. Further studies on larger series of patients and with a longer follow-up are needed to evaluate the effectiveness of this new type of treatment compared with conventional chemotherapies.