BACKGROUND: Mycoplasma pneumoniae is the most frequent cause of respiratory tract infections in schoolaged children and adolescents. For appropriate use of antibiotics, diagnosis of M. pneumoniae infection in routine clinical practice has been based on serology using a single serum sample. We evaluated the seroprevalence of anti-M. pneumoniae-specific antibodies in 500 asymptomatic, healthy persons in Jeonnam Province. METHODS: Sera were collected from 500 healthy persons in Jeonnam Province. Anti-M. pneumoniae antibody titer was measured using a microparticle agglutination assay Serodia Myco II (Fujirebio, Japan) and VIRCELL IgM Mycoplasma ELISA kits (Vircell, Granada, Spain). RESULTS: Anti-M. pneumoniae antibody titers in 500 healthy individuals were 1:20 in 344 (68.8%), 1:40 in 16 (3.2%), 1:80 in 71 (14.2%), 1:160 in 45 (9.0%), 1:320 in 14 (2.8%), and <1:320 in 10 (2.0%). The positive rate of M. pneumoniae IgM antibodies was 3.2% (15/473). The prevalence of IgM was 10.0% in the 7~9 years, 9.1% in the 10~19 years, and 5.0% in the 20~29 years old group, which was significantly higher than that in elderly people. CONCLUSION: Some of healthy people showed a high anti-M. pneumoniae antibody titer (>1:160) and positive IgM, and an assessment of current infection with single serum serology has its limitation for the diagnosis of M. pneumoniae infections.