To clarify the incidence and characteristics of hematopoietic cell transplantation (HCT)-related nephropathy (HCT-N) in Japan, we sent questionnaire letters to 188 hematologic divisions of 91 hospitals and analyzed the responses. Of 2,136 Japanese hematopoietic cell transplant recipients, 51 patients (2.4%) had HCT-N, The early-onset (less than or equal to 30 days after HCT), middle-onset (31 to 120 days after HCT), and late-onset (>180 days after HCT) groups included 20, 16, and 15 patients, respectively. The early-onset group mainly consisted of patients with acute renal failure (ARF) and hemolytic uremic syndrome and/or thrombotic thrombocytopenic purpura, ARF was the dominant type in the middle-onset group. The main phenotype of the late-onset group was nephrotic syndrome, which correlated with chronic graft-versus-host disease (P = 0.008), The total amounts of irradiation for patients with chronic renal failure and urinary abnormality were significantly greater than those for patients with ARF (P = 0.004), The survival rate of the early-onset and middle-onset groups was 47.2%, whereas 87% of patients in the late-onset group survived (P = 0.002), HCT-N is expected to become a serious and important problem in Japan because of the increasing number of HCTs from unrelated donors. (C) 2000 by the National Kidney Foundation, Inc.