Five hundred eighty-three patients and 451 medical personnel of 15 hemodialysis centers were surveyed for hepatitis B infections. Hepatitis B antigen (HB Ag) was detected in 16.8% of the patients and in 2.4% of the medical staff; specific antibody to HB Ag (HB Ab) was detected in 34.0% and 31.3%, respectively. The cumulative prevalence of HB Ag and HB Ab varied widely among the centers. The prevalence of HB Ag or HB Ab in patients was related to duration of dialysis treatment, but not to blood transfusions. Significant differences in prevalence of serologic indicators of hepatitis B infection among various staff categories were not observed. Sixty-one percent of family contacts of dialysis patients with a history of hepatitis B infection were found to have HB Ag or HB Ab.