Twenty-seven patients ranging in age from 15 to 36 years participated in a pilot study, and underwent allogeneic bone marrow transplantation (BMT) for acute lymphoblastic leukemia (ALL) in first complete remission (CR) in four French centers. All patients were grafted from human leukocyte antigen/mixed leukocyte culture (HLA/MLC) identical sibling after conditioning regimen consisting of cyclophosphamide and total body irradiation (TBI). Sixteen patients are alive in persistent first remission, with a median follow-up of 56 months (range, 41 to 82 months). The 6-year Kaplan-Meier probability of disease-free survival (DFS) is 59%. Only three patients relapsed (5, 7, and 7 months after transplantation). These interesting results have led us to propose, in accord with a French multicentric protocol, allogeneic BMT for adults under 40 years of age during the first CR of ALL.