The effect of a deliberate transfusion policy for prevention of primary cytomegalovirus (CMV) infection, consisting of leukocyte-poor red blood cells from random donors and platelets from CMV-negative donors, was studied in 29 CMV-negative negative recipients of an allogeneic (from CMV-negative donors) or autologous bone marrow transplant. All transplant recipients remained CMV-negative with this approach. Such a policy depends on the availability of CMV-negative platelet donors. Siblings from CMV-negative marrow transplantation candidates appeared to be more often CMV-negative than siblings from CMV-positive transplantation candidates (77% versus 34%, p less than 0.001). Selection of CMV-negative blood bank donors for transfusion of blood products is also easy to perform. As a consequence, CMV-negative marrow transplant recipients have a good chance of receiving CMV-negative marrow transplants and blood products and primary CMV infection can thus be prevented by this transfusion policy.