Fanconi anemia is a genetic disorder associated with diverse congenital abnormalities, progressive bone marrow failure, and increased risk of leukemia and other cancers. Affected persons often die before 30 years of age. Bone marrow transplantation is an effective treatment, but there are few data regarding factors associated with transplant outcome. We analyzed outcomes of HLA-identical sibling (N = 151) or alternative related or unrelated donor (N = 48) bone marrow transplants for Fanconi anemia performed between 1978 and 1994 and reported to the International Bone Marrow Transplant Registry. Fanconi anemia was documented by cytogenetic studies in all cases. Patient, disease, and treatment factors associated with survival were determined using Cox proportional hazards regression. Two-year probabilities (95% confidence interval) of survival were 66% (58% to 73%) after HLA-identical siblings transplants and 29% (18% to 43%) after alternative donor transplants. Younger patient age (P .0001), higher pretransplant platelet counts (P = .04), use of antithymocyte globulin (P = .005), and use of low-dose (15 to 25 mg/kg) cyclophosphamide plus limited field irradiation (P = .009) for pretransplant conditioning and cyclosporine for graft-versus-host disease prophylaxis (P = .002) were associated with increased survival. Bone marrow transplants are effective therapy for Fanconi anemia. The adverse impact of increasing age and lower pretransplant platelet count on transplant outcome favors earlier intervention, especially when there is an HLA-identical sibling donor.