Bone marrow transplantation renders patients immunocompetent due to the need for supralethal doses of chemoradiotherapy prior to infusion of the donor stem cells. Multiple immunological deficiencies are seen and patients are at high risk of developing a variety of infections. This period of immunological incompetence usually lasts from 6 to 12 months. In some subsets of patients [those with chronic graft-versus-host disease (GVHD); recipients of unrelated transplants; increasing patient age] persistent T and B cell abnormalities may be seen for years, despite normal serum immunoglobulin levels. This review summarizes a number of trials of intravenous immune globulin (IVIG) therapy to prevent infection following bone marrow transplantation. IVIG has shown benefit in reducing septicaemia, interstitial pneumonia, fatal cytomegalovirus (CMV) disease, acute GVHD and transplant-related mortality in adult recipients of related marrow transplants. Further investigation into dose, schedule and duration of IVIG prophylaxis needs to be conducted.