Five patients (age range 7-14 years) received allogeneic bone marrow transplantation (BMT) for Fanconi anemia (FA). All patients showed progressive pancytopenia associated with congenital malformations. Diagnosis was confirmed by studies of cellular hypersensitivity to the clastogenic effect of the DNA crosslinking agent diepoxybutane. The conditioning regimen consisted of low dose cyclophosphamide (5 mg/kg x 4) and fractionated total body irradiation (167 cGy x 3). For graft-versus-host disease prophylaxis one patient was given cyclosporin alone while the remaining four patients received a combination of cyclosporin and two doses of methotrexate. Marrow was given unmanipulated from HLA-identical siblings. All patients are alive 18-67 months after grafting with Karnofsky scores of 100% and normal hemopoiesis of donor origin. Modifications in transplant protocols such as those here described have resulted in a decreased risk of severe transplant-related complications. These results confirm that BMT is a curative therapy in FA patients and should be considered as a first choice treatment if an HLA-identical donor is available.