The prevalence of serum hepatitis B virus markers was studied in three groups of age- and sex-matched patients: a. 31 patients with liver cirrhosis and hepatocellular carcinoma (c-HCC); b. 31 patients with chronic liver disease (CLD) and c. 62 hospitalized control subjects. The overall exposure rate to the hepatitis B virus was 90% in c-HCC, 80% in CLD and 58% in control subjects. The prevalence of hepatitis B surface antigen (HBsAg) was 29%, 13% and 1.6% in the three groups, respectively. The prevalence of hepatitis B surface antibody was significantly lower in c-HCC (9.6%) than CLD (42%) and control subjects (40%). The serological evidence of continuous viral replication (HBsAg positivity or isolated high titre hepatitis B core antibody positivity) was more common in c-HCC (39%) than CLD (12%) and control subjects (1.6%). The prevalence and patterns of aggregation of serum hepatitis B virus markers were similar in the 31 patients with c-HCC and in 11 patients with HCC without concomitant liver cirrhosis (n-HCC). In conclusion, the overall exposure rate to the hepatitis B virus is similar in c-HCC and CLD. However, serological evidence of continuous viral replication is more common in the former group. A defective clearance of the hepatitis B virus in hepatocellular carcinoma is a possible explanation of the phenomenon. The strength of the association between hepatitis B virus infection and hepatocellular carcinoma appears to be similar in c-HCC and n-HCC.