Malignant hemopathies and immune deficiencies are the main indications for allogeneic bone marrow transplantation in children. Among the former, the most common condition is acute lymphoblastic leukemia, in which a bone marrow transplant can be performed during the second or first complete remission (CR). Thirty to 50% and 60 to 75% of these grafts, respectively, are successful. The success rate is 50 to 70% among patients with acute myeloblastic leukemia grafted during the first complete remission, and among patients with chronic myeloid leukemia grafted during the chronic phase. Severe medullary aplasia and Fanconi disease are undoubtedly good indications for bone marrow transplantation, which has a 60 to 70% success rate. Severe combined immune deficiencies (SCID) and Wiskott-Aldrich disease are also good indications for HLA-identical bone marrow transplantation, which is successful in 60% of cases. Among the metabolic diseases, good results have been obtained only in Hurler disease and Gaucher disease. Questionable indications include thalassemia, Blackfan-Diamond disease, and chronic granulomatous disease. Results are disappointing in most metabolic diseases, as well as in non-HLA-identical transplantations in diseases other than SCID.