Three-hundred forty-one HBsAg-positive family members of 152 patients with chronic hepatitis B virus infection (47 asymptomatic carriers, 59 with chronic hepatitis, 17 with cirrhosis and 29 with hepatocellular carcinoma) were prospectively studied to determine the morbidity and mortality from chronic hepatitis B virus infection in the family members of patients with malignant and nonmalignant hepatitis B virus-related chronic liver diseases. Most of the family members had no history of acute hepatitis, were asymptomatic and were unaware of their carrier status. However, 5.3% had stigmata of chronic liver disease, 6% had serum ALT levels that exceeded two times the upper limit of normal and 78% of those who had biopsies had chronic hepatitis with or without cirrhosis. During a follow-up period of 12 to 90 mo (median = 39 mo), 3% had symptoms of chronic liver disease; 24% had transient, recurrent or persistent elevation in serum ALT levels, 1.4% had cirrhosis and 1% had hepatocellular carcinoma. Neither hepatocellular carcinoma in the index patient nor a previous history of hepatocellular carcinoma in the family was associated with an increase in the morbidity and mortality from chronic hepatitis B virus infection in the HBsAg-positive family members.