X-linked SCID (XSCID) is a lethal immunodeficiency dIsease unless cured by bone marrow transplantation. Although infants lacking an HLA identical donor have successfully received T-cell depleted haploidentical transplants to restore immunity, strategies which significantly depleted donor T cells often result in delayed engraftment and/or severe graft versus host disease (GVHD). We successfully restored T-cell immunity in five infants with XSCID by using parental bone marrow cells with a defined dose of T cells. The children received similar preconditioning regimens of busulfan and cyclophosphamide. T-cell depletion of donor cells was carried out by centrifugal elutriation of harvested bone marrow. An average dose of 2.4 (+/- 1.5) × 108/kg nucleated cells containing 2.1 (+/- 0.3) × 106/kg CD34+ stem cells and 4.1 (+/- 1.1) × 105/kg T cells was infused following elutriation. Engraftment of donor cells occurred at 15 (+/- 4) days in the five children. Mild (grade I) GVHD occurred in four children and two children failed to engraft the donor B cells. Our strategy to provide a limited number of donor T-cells (2-5 × 105 cells/kg) using elutriated marrow depleted of T-cells is an effective therapy for the treatment of XSCID.