Gaucher disease has been treated by allogeneic bone marrow transplantation (BMT), however, severe bone involvement that is probably the most disabling aspect of this disease is difficult to reverse. Other problem of BMT is the use of intensive preconditioning that adversely affects growth and development of the patients. In this study, a patient with type I Gaucher disease was treated by allogeneic BMT from HLA-matched sibling donor. However, the treatment resulted in late graft failure and the patient developed severe bone involvement. Fifty months after the first BMT, the patient was treated by allogeneic peripheral blood stem cell (PBSC) transplantation without preconditioning. Recombinant human granulocyte-colony stimulating factor (rhG-CSF) was used to mobilize PBSC. Cyclosporine A (CyA) was administered for the prophylaxis of graft-versushost disease (GVHD). Full donor-derived hematopoiesis was obtained, and clinical symptoms including severe bone involvement improved completely with increased glucocerebrosidase activity. It was shown that an engraftment could be obtained without intensive preconditioning when a recipient receives an rhG-CSF-mobilized PBSCs infusion as a secondary transplant. Another important finding of this study is the complete reversal of severe bone involvement by the supply of abundant glucocerebrosidase from high proliferating PBSC graft.