Using non-myeloablative conditioning, allogeneic hematopoietic stem cell transplantation (HSCT) was conducted in 43 ALL patients in a CR2. The median age of the patients was 19 years. Patients received oral busulfan 4 mg/kg/day for 2 days; i.v. cyclophosphamide 350 mg/m(2)/day for 3 days; and i.v. fludarabine 30 mg/m(2)/day for 3 days. Oral cyclosporin A 4 mg/kg was started and methotrexate 5 mg/m(2) was delivered on days 1, 3, 5 and 11. The median CD34+ cell dose received was 5.0 x 10(6)/kg. The medium time to achieve a granulocyte count above 0.5 x 10(9)/l was 14 days. Thirteen patients were alive 30-1050 days after the HSCT. The 3-year overall survival rate was 30%. Ten patients (23%) developed acute GVHD, whereas eight patients (18.6%) developed chronic GVHD. Thirty patients died between days 47 and 1050 after the HSCT, most of them (70%) because of an ALL relapse. One hundred-day mortality was 15%, whereas transplant-related mortality was 21%. These results are inferior to those obtained using the same allografting method in other leukemias, probably as a consequence of poor susceptibility to the graft-versus-leukemia effect of the ALL cells beyond first remission as compared with other hematological malignancies.