42 patients suffering from terminal leukaemic lymphosarcoma were treated as acute lymphoid leukaemia patients. 26 entered apparently complete remission (CR). They were submitted to complementary cell reducing treatment comprising systemic and intrathecal chemotherapy and radiotherapy on the CNS and on the lymphosarcomatous masses that had been detected at the beginning of leukaemic conversion. Eight relapsed during this treatment and 18 were still in CR at the end of it: nine were submitted to active immunotherapy (BCG + C. granulosum + irradiated allogeneic leukaemic lymphosarcoma cells): five out of the nine have remained free of disease for between 13 to 66 months. Nine served as controls: all except two, who are still at the beginning of the trial, have already died from leukaemic manifestations.