Epidemiologic and serologic data on 137 household contacts of 51 chronic carriers of HBsAg and 111 household contacts of 38 controls who were negative for serologic markers of hepatitis B virus (HBV) were obtained from March 1990 to August 1991. Using this data, possible routes of intrafamilial transmission of hepatitis B virus among household contacts of chronic carriers of hepatitis B surface antigen (HBsAg) were evaluated and analyzed. The HBsAg prevalence among the household contacts of carriers was 14. 1% (95% CI 7.8-24.0) compared to 0.0% (95% CI 0.0-7.0) among those of controls (P<0.01). The offspring of carriers showed significantly higher risk of HBV infection(relative risk; 6.6). Sharing of towels and handkerchieves, and drinking vessels was associated with an increased risk of HBV infection via intrafamilial transmission in Korea (relative risk 11.5 for towel and handkerchief, 12.1 for drinking vessels).