The role of bone marrow transplantation is to restore lymphohematopoietic function of a recipient whose marrow has been destroyed, either by disease or by the preparative therapy employed in an attempt to eradicate the patient's lymphohematopoietic malignancy. The restoration of lymphohematopoietic function through the donor graft occurs in stages, requires several months, and is often not completed until 1 to 2 years after transplantation. These sequential steps of immuno-reconstitution are associated with a number of definable and predictable immune deficiencies and seem to be responsible for the pattern of complications that emerges after transplantation. Most of these complications are either the result of, or associated with, infections that also occur in an almost predictable pattern. In the various phases of immune deficiency following sequentially after transplantation, the humoral immune system is greatly affected, thus raising the possibility that passively administered antibodies in the form of immune globulin therapy might be beneficial in all phases of the marrow transplant procedure. This paper attempts to summarize the use of immune globulin preparations in clinical bone marrow transplantation, showing the rationale for and some of the results of therapeutic immune globulin administration.