For many years blood transfusions have been implicated as a source of transmissible cytomegalovirus (CMV). In spite of numerous reports on this problem many questions have never been adequately answered. These questions are: 1) Is CMV really transmissible in the blood? 2) If CMV is transmitted via blood, can this be detected and/or prevented either by screening procedures in the donors or by methods of blood preparation? Are these methods cost effective? 3) If CMV transmission can be prevented, which classes of patients should receive CMV free blood? Because additional data area required to adequately answer these questions we propose the following: 1) To prospectively determine the incidence of transfusion associated CMV infections (including primary, reinfection, and reactivated latent infection) in both nonimmunocompromised and immune deficient blood recipients. This will include the use of restriction enzyme analysis of CMV DNA on paired donor recipient CMV isolates. 2) To determine the clinical significance of CMV infection in these patients. 3) To determine which classes of patients would best benefit from reducing the risk of CMV acquisition from transfusion besides the already established classes of low birth weight infants and transplant patients. These patients will include surgical patients of all types, and immunocompromised oncology patients. 4) To evaluate CMV viruria, and the levels of a variety of specific anti CMV immunoglobulins as a means of determining which blood donors are capable of transmitting CMV. 5) To study the biological and biochemical characteristics of CMV associated with leukocytes. This study will provide data for defining and preventing significant transfusion acquired CMV disease.