BACKGROUND: Several reports have recently suggested a positive correlation between components of metabolic syndrome (MS) or insulin resistance syndrome (IRS) and markers of the acute-phase response, including C-reactive protein (CRP). These results imply that MS and type 2 diabetes are the results of ongoing inflammatory process. Whether estrogen plays a beneficial role in preventing atherosclerosis has been a matter of controversy. The objective of this study was to evaluate the relationship between the serum levels of estradiol (E2) and the components of the MS and CRP in nondiabetic subjects of Ansan Health Study (AHS). METHODS: Eight-hundred and ninety-one healthy non-diabetic women aged over 18 years were enrolled. After measurements of the anthropometric and metabolic parameters, correlation and multiple linear regression analyses were performed with regard to the CRP level, as a dependent variable, and with regards to age, blood pressure (BP), body mass index (BMI), lipid profiles, fasting plasma glucose levels, HOMA-IR and fat content as independent variables. RESULTS: In the multiple linear regression analysis, the CRP concentration was found to be independently associated with the E2 level, total fat content, leukocyte counts, and total cholesterol level in all subjects and the serum E2 levels was correlated with age, HOMA-IR, total cholesterol and the CRP level. When subjects were grouped according to their number of MS or IRS components, the CRP levels were found to show statistically significant differences between the MS and IRS groups. CONCLUSION: As a marker of chronic inflammation, the serum CRP level was independently associated with the components of MS and IRS. Also, the serum CRP and E2 levels were positively correlated. These results suggest that estrogen and CRP might play some independent roles in chronic inflammation which is a part of MS and IRS.