Since 1979, a total of 17 patients with Wiskott-Aldrich syndrome have undergone allogeneic bone marrow transplantation at Memorial Sloan-Kettering Cancer Center. Eleven patients received marrow from either human leukocyte antigen (HLA) genotypically identical siblings (nine patients) or an HLA phenotypically identical parent (two patients). Six patients received marrow grafts from HLA-disparate parents. Cytoreduction was accomplished with busulfan and cyclophosphamide for the HLA-identical recipients and total-body irradiation followed by high-dose cytarabine therapy in the mismatched recipients. All 11 recipients of HLA-identical marrow had successful grafts, and 10 of 11 are alive and well 28 to 145 months after transplantation. One patient died 10 months after transplantation of chronic graft-versus-host disease and interstitial pneumonitis caused by cytomegalovirus. Only one of the six mismatched graft recipients survives, 52+ months after transplantation; the other patients have died of extensive chronic graft-versus-host disease (one patient), lymphoma (three patients), or progressive pancytopenia accompanying Candida sepsis (one patient). Thus bone marrow transplantation represents the treatment of choice in patients with Wiskott-Aldrich syndrome who have an HLA-identical donor. However, our approach for patients lacking a histocompatible family donor requires modifications to overcome allogeneic resistance and decrease the posttransplantation immunoincompetence in these patients.