Little is known about the prevalence of naturally acquired IgG antibodies to the capsular polysaccharides of Streptococcus pneumoniae (pneumococcal IgG) in Korea. In the present study, we investigated transplacental transfer and age-related levels of pneumococcal IgG to provide background seroepidemiologic data for S. pneumoniae in Korea. One hundred thirty eight sera were assayed by ELISA for IgG to pneumococcal polysaccharide capsular serotypes 14 and 19, the predominant serotypes for under 15 yr of age in Korea. The subjects were divided into 7 subgroups according to age. The cord/maternal geometric mean titer of pneumococcal were 4.47±5.88/5.21 ± 5.88 for serotype 14, and 4.68 ± 5.55/6.55 ± 6.92 for serotype 19 (mean ± standard deviation, µg/mL). After birth, the geometric mean titers of pneumococcal IgG for serotypes 14 and 19 expressed in µg/mL were 1.18±2.12 and 1.41±2.17 in the 0-6 months group, 0.27±0.19 and 0.69±0.93 in 7-12 months, 0.21±0.22 and 0.64±1.32 in 1-2 yr, 0.69±0.78 and 2.65±2.46 in 3-6 yr, 2.52±2.72 and 8.29±4.24 in 7-10 yr, respectively. In conclusion, reduced transplacental transfer and very low serum concentrations of pneumococcal IgG may contribute to the susceptibility of neonates, infants, and young children to S. pneumoniae infection.