Premature infants who require multiple blood transfusions have a 15-30 percent incidence of cytomegalovirus infections. Many of these infections result in severe disease, with a mortality of about 20 percent. In theory, the infection could be avoided by using blood and blood products exclusively from CMV antibody negative donors. The use of such blood is impractical because it would require the rejection of approximately 40 percent of all blood donors. Studies had suggested that passively acquired antibody could reduce the incidence of disease in exposed neonates. This provided the rationale for the use of passive immunization with hyperimmune globin in premature infants likely to require multiple transfusions. Lots of high titer CMV immune globulin suitable for intravenous administration were prepared using a technique of screening outdated blood bank plasma for units with high levels of antibody to CMV.