Persistent organochlorine pesticides (OCPs) are well known to accumulate in environment and to instigate disruptions in endocrine system. In the present study, 18 kinds of OCPs were bio-monitored from 1904 adult serums. Analysis was performed with headspace gas chromatography (HS-GC) which has the advantage to require small volume of serum (1mL) without complex pretreatment and 13C isotope labeled internal standard mix was used for quantitation. As a result, eleven out of 18 OCPs, including hexachlorobenzene (HCB) and dichlorodiphenyltrichloroethane metabolites (DDTs) were detected. HCB was the most frequently detected OCP (8.0%) with an average concentration of 1.74ngg−1 lipid (2.10ngg−1 lipid–99.80ngg−1 lipid). p,p′-Dichlorodiphenyldichloroethylene (p,p′-DDE) had the highest average concentration of 21.65ngg−1 lipid (12.80ngg−1 lipid–2270ngg−1 lipid) and was detected from 7.5% of serum samples. The average concentration of ∑DDT metabolites was 32.04ngg−1 lipid (6.61ngg−1 lipid–2800ngg−1 lipid) with detection frequency of 9.0%. Results interpreted with respect to age groups showed increase in ∑OCPs and ∑DDTs concentrations as age increases, except for the 20. Results interpreted with respect to gender, in general, illustrated higher detected concentration of OCPs in male serums than in female serums; however, the result trend was reversed in age group of the sixties. The above results will be applicable to health impact assessment of Koreans in relation to environmental contaminations.