This study was conducted to determine the rate of detection of serum hepatitis B virus (HBV) DNA in hepatitis B surface antigen (HBsAg)-negative decompensated cirrhotic patients who had hepatitis B core and/or surface antibodies (anti-HBc and/or anti-HBs), and to compare the outcome of HBsAg-positive cirrhotic patients who did or did not clear HBsAg during follow-up. Six (5%) of 121 HBsAg-positive cirrhotic patients lost HBsAg after 0.2 to 17.1 years (mean, 9.1 +/- 6.2 yr) of follow-up. The cumulative rates of loss of HBsAg at 1, 5, 10, and 15 years were, respectively, 1.3%, 1.3%, 7.4%, and 44.5%. Compared with the patients who remained HBsAg-positive, those who lost HBsAg had milder disease at presentation and significantly longer survival. Of the patients who lost HBsAg, 83% had improvement in liver function after the loss of HBsAg, and all were alive at the time of writing (0.8 to 5.7 years after loss of HBsAg), whereas 27% of those who remained HBsAg-positive had died and 29% had deterioration in liver function. The rate of detection of serum HBV DNA by polymerase chain reaction (PCR) assay was higher in HBsAg-positive cirrhotic patients who lost HBsAg:67% versus cirrhotic patients who had no previous history of chronic HBV infection; 16% (cryptogenic) and 29% (hepatitis C virus and/or alcohol-induced liver disease). In summary, we found that using PCR, serum HBV DNA can be detected in 28% of HBsAg-negative cirrhotic patients who were studied, but the pathogenic significance of such small amounts of virus is not clear.(ABSTRACT TRUNCATED AT 250 WORDS)