We evaluated relapse-free survival and the incidence and type of complications in 17 patients aged 40 or older with chronic myelogenous leukemia, acute myelogenous leukemia, or lymphoma who underwent allogeneic marrow transplantation following busulfan 16 mg/kg and cyclophosphamide 120 mg/kg. Nine patients are diseasefree survivors 5–38 months (median 26 months) following transplantation. The incidence of grades II-IV acute graft-versus-host disease was 35%. No significant difference was detected in the incidence of GVHD or interstitial pneumonia between patients aged 40 and older and a group of younger patients transplanted over the same time period. These observations should encourage consideration of allogeneic marrow transplantation in older patients and suggest that this busulfan-cyclophosphamide regimen is a promising alternative to regimens containing total-body irradiation in older individuals.