We investigated the frequencies and predictive factors of prolonged renal failure (PRF) in a retrospective study of 181 consecutive patients undergoing allogeneic hematopoietic stem cell transplantation. Twenty-six patients (23% of long-term survivors) developed PRF. We identified 4 independent prognostic factors; cytomegalovirus infection and chronic graft-versus-host disease appeared as major risk factors for PRF.