Varicella-zoster virus (VZV) causes chickenpox and herpes zoster. Korea is assumed to have a high seroprevalence of VZV, although data are scant. A cross-sectional and age-stratified study was conducted to investigate the seroprevalence of VZV in different ages in the South Korean population. Four medical institutions were chosen in the southwestern area of Seoul in the vicinity of Gyeonggi-do. Serum samples were obtained at each institution from consenting patients during April-August, 2008. Anti-VZV IgG antibody was measured by an enzyme immunoassay. Of the 887 patients, 87.6% had anti-VZV IgG antibody. The prevalence of anti-VZV IgG antibody was 75% during the first 3 months after birth, but was only 13.6% 12 months after birth. Anti-VZV IgG antibody prevalence increased, first at 1-2 years of age, and then at 5-6 years of age. The seroprevalence rate exceeded 90% in subjects over 11 years of age. The results show that the seroprevalence of VZV is relatively high in the South Korean population. A study on the rate of varicella vaccination and the vaccine's efficacy in South Korea is warranted.