BMT was carried out on a patient with DiGeorge syndrome who suffered recurrent infections after birth. At 13 months of age, 8.0 x 10(8)/kg of bone marrow nuclear cells were infused from an HLA-identical sibling using only anti-thymocyte globulin to prevent rejection. Donor DNA was not detected on microsatellite polymorphism by PCR. At 19 months of age, a second BMT from the same donor was carried out using busulfan and cyclophosphamide as conditioning. DNA examination of bone marrow showed chimerism at day 18 and complete donor origin at day 28. Seven months post-BMT, the numbers of CD3-, CD4- and CD8-positive cells were in the normal range. BMT is thus an effective therapy for DiGeorge syndrome.