Between March 1984 and March 1995, 76 patients with advanced acute myelogenous, acute lymphoblastic, or chronic myelogenous leukemia underwent allogeneic marrow transplantation from HLA-identical or one-antigen mismatched sibling or unrelated donors. Patients received a preparative regimen consisting of busulfan 16 mg/kg and cyclophosphamide 120 mg/kg or busulfan 14 mg/kg, cyclophosphamide 120 mg/kg and etoposide (VP-16) 50 mg/kg. For GVHD prevention, patients received cyclosporine with either methotrexate or steroids or FK506 with methotrexate. Fourteen patients were leukemia-free survivors at a median of 6.5 years (range 1-11 years) following transplantation. For the group as a whole, the estimated leukemia-free survival (LFS) at 5 years is 20% (95% confidence interval 10-30%). Ten of the 14 leukemia-free survivors developed acute GVHD greater than grade II and chronic GVHD and two developed only chronic GVHD. Significantly better relapse rates and disease-free survival were associated with the development of acute and/or chronic GVHD. In the absence of acute GVHD and/or chronic GVHD, patients who underwent transplantation for advanced leukemia, after preparation with Bu/CY or Bu/CY/VP-16, were very likely to experience disease recurrence. Novel strategies designed to promote development of GVHD present a promising area for investigation to improve outcome in patients with leukemia at high risk for relapse.