Purpose : The incidence of measles was gradually decreased since 1963 when measles vaccination was firstly developed and liscenced in the world. But, recently the outbreaks of measles in infants and school children have been reported despite of wide spread use of measles vaccination. This study was performed to evaluate the efficacy of measles vaccination and the necessity of revaccination in Korean infants and children. Methods : 168 subjects of mothers and neonates, infants and children were enrolled in this study during the periods of 10 months from March to December in 1995. Measles specific IgG in the sera of mothers and children was measured using EIA kit (Sigma Co., MO, USA). Antibody titer of over or equal to 110 AU/ml was considered positive. Results : The results obtained were as follows. 1) Values of measles specific IgG in the sera of mother and neonate were 82.9 AU/ml and 89.3 AU/ml respectively and were rapidly decreased within 6 month after birth. Positive antibody levels (${geq}$ 110 AU/ml) were observed in only 25 % of neonates. 2) In vaccinated children, values of measles specific IgG were 117.4 AU/ml in 9~15 month group, 76.9 AU/ml in 3~6 year group and 79.5 AU/ml in 10~15 year group after either one or two times of measles vaccination. Positive antibody levels in vaccinated children were observed in 57.7% of 9~15 month group, 38.4% of 3~6 year group and 34.7% of 10~15 year group. Conclusion : These results suggest that primary measles vaccination before 6 months of age can be considered and revaccination of measles should be recommended before 3~6 years of age. Further studies will be needed to clarify the reasons of high proportion of primary measles vaccination failure and to established the appropriate schedule of measles vaccination in korean infants and children.