patients with transfusion-associated and other hepatitis [1-3], and the Herpes group of viruses, specifically cytomegalovirus (CMV) [4-7] and, to a lesser extent, Epstein-Barr virus (EBV) [8]. The association between hepatitis and HAA is strong; this antigen has been found in the serum of up to 80 96 of patients with transfusion-associated hepatitis but in only 0.196 of normal persons in this country [9, 10]. In contrast, the association between CMV infection and hepatitis is less well established. Evidence for hepatitis due to CMV has consisted, with a few exceptions [11], of a serologic response or isolation of virus from patients who developed hepatitis. While evidence for infection with CMV in patients with hepatitis has frequently been found, there has been insufficient emphasis on the study of the incidence of infection with CMV in appropriately matched controls, i.e. persons who do not have hepatitis. Furthermore, there are only two published reports that deal with the relative importance of HAA and CMV in the same group of patients [12, 13]. However, only six patients with hepatitis were studied in one report [12], and all of