Bone marrow transplantation (BMT) is the only curative therapy available for hemoglobinopathies. BMT was performed on a young child with sickle cell anemia (SCA) after approximately 9 months of transfusion therapy following her initial stroke. The patient received a matched sibling donor (sickle trait) BMT. The conditioning regimen consisted of busulfan 4 mg/kg/day x 4, cyclophosphamide 50 mg/kg/day x 4. Graft vs. host disease prophylaxis was daily cyclosporine for 6 months. There were no significant complications during BMT. Engraftment occurred on day +17 and the patient was transfusion independent since day +45. Pre-BMT cerebral arteriography showed multiple stenotic cerebral vessels and a moya-moya pattern. Perfusion MRI demonstrated reduced capillary perfusion. Approximately 170 days after BMT the patient experienced episodes of transient left-sided weakness and speech problems. Neuroimaging revealed progression of large vessel pathology by angiography despite significant improvement in cortical perfusion (MR perfusion scan). Molecular analysis by PCR and DNA fingerprinting confirmed absence of mixed mosaicism. Rheologic evaluation showed normal corrected bulk viscosity. It is possible that progression of large vessel pathology and return of clinical symptoms in the face of normal rheologic parameters may be due to worsening of the already damaged cerebral vessels by the BMT conditioning regimen. Further evaluations of patients with SCA undergoing BMT after a stroke are needed to answer this question.