We evaluated transplant-related mortality (TRM), leukaemia relapse, leukaemia-free survival (LFS) and overall survival (OS) in patients receiving busulphan and cyclophosphamide (BuCy) or cyclophosphamide and total body irradiation (CyTBI) prior to allogeneic bone marrow transplantation (BMT) for acute myelogenous leukaemia (AML) in first remission. Outcomes of 381 human leucocyte antigen (HLA)-matched sibling transplants using BuCy were compared with 200 transplants using CyTBI performed between 1988 and 1996. The incidence of hepatic veno-occlusive disease was higher with BuCy (13%) than with CyTBI (6%) (P = 0.009). Risks of acute and chronic GVHD were similar. In multivariate analysis, relapse risk was higher in the BuCy group [relative risk (RR) = 1.72; 95% confidence interval (CI), 1.05-2.81; P = 0.031]. Eleven of 373 evaluable patients in the BuCy group had a central nervous system relapse in contrast to none of 194 evaluable patients in the CyTBI group (P = 0.016). There were no differences in TRM, LFS and OS. CyTBI conditioning may lower relapse risk but produces comparable TRM, LFS and OS to BuCy for HLA-matched sibling transplantation in first remission AML.