To assess the prevalence, risk factors, clinical causes and outcome of acute renal failure (ARF) following bone marrow transplantation (BMT), a retrospective analysis of 275 patients was undertaken. ARF was diagnosed in 72 patients (26%) and occurred in 81.9% within the first month. The three main clinical causes were multifactorial (36%), nephrotoxic (29%), and veno-occlusive disease of the liver (VOD) 15%. The prevalence was higher in allogeneic BMT (36%) than in autologous BMT (6.5%). Risk factors related to the development of ARF wee preexisting VOD and age older than 25 years. Logistic regression in allogeneic BMT confirmed this association (VOD, odds ratio 3.8; age offer than 25, odds ratio 1.9). Underlying disease, graft-versus-host disease, sepsis, conditioning therapy, and sex were not associated with ARF. Seventeen cases of ARF required hemodialysis (24%) mainly in association with VOD (70.5%). The overall morality from ARF was 45.8%, the dialyzed group having the highest mortality (88%). Survival in the ARF group was continuously worse up to 3 months and the actuarial survival at 10 years was 29.7 versus 53.2%. We conclude that ARF is a common complication mainly in allogeneic BMT and carries a grave prognosis. VOD and age were risk factors for ARF.