In this retrospective analysis of allogeneic bone-marrow transplantation (BMT) carried out between 1969 and 1985 at fourteen European centres in 162 patients with sixteen different types of inherited immunodeficiencies and osteopetrosis, the overall survival with functional grafts was 51.7% (85 patients), with a minimum follow-up of 5 months. In patients with severe combined immunodeficiency HLA-matched (n = 41) and T-cell-depleted HLA-mismatched BMT (n = 46) resulted in 68% and 57% disease-free survival, respectively; after HLA-mismatched transplants, older age (greater than 6 months) and adenosine-deaminase deficiency resulted in poorer survival. Eight other lethal immunodeficiencies, including profound T-cell deficiencies, Wiskott-Aldrich syndrome, Kostmann syndrome, LFA-1/CR 3/p150,95 deficiency, and Chediak-Higashi syndrome as well as malignant osteopetrosis, have been successfully treated by BMT. In this group, survival with functional graft was 47% with HLA-matched and 29% with T-cell-depleted HLA-mismatched BMT. Engraftment failure was the major complication in this group. Poorer prognosis was associated with older patients, profound T-cell deficiencies, and the degree of HLA incompatibility.