The aim of this study was to determine the age-specific rubella seroprevalence and the related factors in Korean children. Subjects of the study were 5393 students from 8 elementary schools in Gyeonggi Province, Korea. Questionnaire surveys with blood sampling were conducted in 1993, 1996, and 1999. ELISA tests, used to detect rubella specific IgG antibody, were Imx (R) (Abbott, U.S.A.) in 1993 and 1999, and Enzygnost (Behring, Germany) in 1996. The age-adjusted rubella susceptibility rate was 22.9% (95% CI: 22.8-23.0%) and it increased with age from 14% to 28%. The susceptibility rates of vaccinees, nonvaccinees, and the unknown group were 21%, 35%, and 27%, respectively (p=0.000). The rates by parental education levels for elementary and below, middle school, high school, and college and over were 37%, 26%, 24%, and 20%, respectively. The geometric mean titers (GMTs) of nonvaccinees, the unknown group, and vaccinees were 47 IU/mL, 42 IU/mL, and 37 IU/mL, respectively (p=0.000). The susceptibility level was too high to prevent the rubella epidemic in Korea, which necessitates a programme that will enhance the coverage for 1st and 2nd MMR vaccination among school children. In particular, more attention should be paid to the vaccination of the children whose parental education level is relatively low.