The aim of the study was to evaluate the safety, immunogenicity, and possible therapeutic effect of hepatitis B vaccine in patients with chronic hepatitis C. The subjects studied included three groups: group I, 26 patients with chronic hepatitis C who were susceptible to hepatitis B virus infection; group II, 35 healthy subjects who were susceptible to both hepatitis B and hepatitis C virus infection; and group III, 30 patients with chronic hepatitis C receiving no hepatitis B vaccination as controls. Three 20 microg/dose of recombinant hepatitis B vaccines were given to subjects of groups I and II in months 0, 1, and 6. Blood samples from the subjects were collected before and 1 month after each dose of vaccination for serological testing. The subjects of groups I and II had similar antibody to hepatitis B surface antigen (anti-HBs) response rates after the first (30.8% vs. 17.1%), second (61.5% vs. 60.0%), and third (88.5% vs. 91.4%) doses of vaccination. Also, their geometric mean titers of anti-HBs did not differ much when vaccination completed in 7 months (360 vs. 581 mIU/ml). During vaccination period, patients with chronic hepatitis C demonstrated no significant change of serum cytokines and HCV RNA levels, but significantly lowered ALT levels after three doses of vaccination. Hepatitis B vaccination is safe and immunogenic in patients with chronic hepatitis C. It did not significantly affect their levels of HCV RNA, but tended to lower ALT levels.