Eleven children were transplanted in our BMT Unit. All but one received standard IVIG preparations in doses of 100 mg/kg b. w. regularly on days before and after transplantation -1, +14, +28, +60 and +90, respectively, and anti-CMV hyperimmune globulin (Cytotect) was given to six patients in the same doses, respectively. In spite of the severe immunodeficiency bacterial infections were verified only in four patients, and CMV infection in three. New infection only occurred in two of the three patients, who hadn't been given CMV prophylaxis, while in the group of six children having been given Cytotect prophylaxis only one became infected from endogenous reactivation of CMV. Therapeutic application of immunoglobulin compounds were used in four of our transplanted patients. Two of them suffered from sepsis during transplantation, one from protracted immunoneutropenia and one from CMV antigenaemia after the transplantation, respectively. Our conclusion is that the administration of immunoglobulins may contribute to the prevention of infections and to the treatment of some complications in BMT recipients. Anti-CMV immune globulin seems to be more effective than standard IVIG in the prevention of CMV infection.