Of 65 renal hemodialysis units surveyed prospectively by the Center for Disease Control in the four-year period 1967 to 1970, fifty-three reported 355 cases of viral hepatitis—260 in hemodialysis patients and 95 in hemodialysis unit staff members. The incidence of infection in 1970 for center-based patients and staff was 4.4 cases and 3.4 cases, respectively, per 100 persons at risk. Almost 70% of the hemodialysis patients were anicteric; many of these cases would not have been detected if periodic serologic screening for hepatitis B antigen or liver-function tests had not been performed routinely. On the other hand, 85% of staff members with hepatitis were jaundiced, and 74% required hospitalization. Although accidental needle punctures prior to hepatitis were reported by many staff, other types of exposures were common, and nonparenteral transmission probably occurred. © 1973, American Medical Association. All rights reserved.