Fanconi anaemia, an autosomal recessive constitutional aplastic anaemia, seems to be related to a DNA repair mechanism defect. Bone marrow transplantation is sthe only treatment which can cure these patients. Previous attempts at BMT have shown an increased sensitivity to Cyclophosphamide used for the conditioning. Such a sensitivity has also been observed in vitro when Fanconi anaemia cells were incubated with alkylating agents. We have tested the in vivo radiosensitivity and cell repair after skin contact radiotherapy to calculate the irradiation dose which could be tolerated by FA patients. Eight patients have been tested and the results confirmed the suspected increased radiosensitivity in the majority of patients. Following these results, four patients were conditioned with low dose Cyclophosphamide (20 mg/kg) associated with 5 Grays thoraco-abdominal irradiation. All had a take and no major complication of the conditioning regimen. All are alive in good condition from day 51 to day 330 after transplant. Oesophagitis was one major unexpected complication. This study confirms the possibility of curing FA patients with BMT when the conditioning regimen is modified according to the pathophysiology of the disease.