Allogeneic bone marrow transplantation was carried out on an 11-year-old boy with chronic granulomatous disease and severe chronic pulmonary insufficiency of restrictive type. After preparative regimen with busulfan (13 mg/kg) and cyclophosphamide (200 mg/kg), the patient received marrow cells from his HLA-identical and MLC-nonreactive sister. Durable sustained engraftment of donor hematopoietic and lymphoid populations occurred, as documented by analysis of genetic markers and complete reversal of the neutrophil function defect. No episode of infection occurred in the post-transplant course and, currently, 40 months after transplantation the patient is in excellent health and growing normally and showing an increasing improvement of his respiratory capacity. The successful outcome in this patient demonstrates that marrow transplantation is at present the only curative approach for this congenital disorder of neutrophil function.