OBJECTIVES: The incidence of clinical hepatitis A has increased in young Korean adults since the mid-1990s. Although hepatitis A vaccinations have been administered in private clinics over the past 10 yr, no data exist on the vaccination rate and relating factors. METHODS: In 2005, a population-based survey of 12-35-month-old children was carried out in Nonsan, Korea. An interview survey was completed for 71.3% of the children. All data came from a vaccination card or confirmation from a provider. RESULTS: The hepatitis A vaccination rate was 42.3% for > or =1 dose and 24.7% for 2-dose. The results of the multivariate regression analysis for the hepatitis A vaccination showed that the second (OR=1.6) and third and successive children (OR=3.3) were less often immunized than the first child. Low economic status (OR=1.6), rural area (OR=1.5) and employed mother (OR=1.5) were also correlated with a lower vaccination rate. The hepatitis A vaccination rate was significantly lower in children who had no other vaccinations: measlesmumps-rubella (OR=2.8 for > or =1 dose and 7.3 for 2-dose), varicella (OR=20.2 and 22.0, respectively) and Haemophilus influenza type b (OR=14.3 and 13.3, respectively). CONCLUSION: To prevent outbreaks of clinical hepatitis A by enough herd immunity, a vaccination should be included in the National Immunization Program and a vaccination policy developed and implemented that can overcome the barriers to immunization such as late birth order and a mother's employment.