Objectives: The purpose of this study was to determine whether women with PCOS have greater subclinical atherosclerosis and evaluate the relationship to risk factors for atherosclerosis. Methods: Women with PCOS(n=24) and age and body mass index(BMI)-matched cycling women(n=16) as control group underwent carotid scanning for the measurement of the IMT. We compared IMT and plaque between cases and controls, assessed some risk factors for atherosclerosis, and analyzed factors affecting IMT. Results: There was no difference between the groups in waist-hip ratio(WHR) and in the levels of total cholesterol, triglyceride(TG), LDL, Lp(a), fibrinogen, homocystein, plasminogen activator inhibitor 1. However, HDL was significantly lower, and systolic and diastolic blood pressure, fasting blood sugar or insulin concentration and IMT was significantly higher in PCOS group than control group (51.1±11.6 vs 60.4±10.0mg/dl, 119.4±12.5 vs 109.0±11.6mmHg, 79.1±11.1 vs 68.9±7.8mmHg, 93.6±11.1 vs 85.0±5.9 mg/dl, 8.9±5.2 vs 5.0±3.3pU/ml, 0.57±0.12 vs 0.49±0.11mm respectively, all p<0.05). In the analysis of correlation between the IMT and clinical characteristics, PCOS status, BMI, systolic and diastolic blood pressure, fasting blood sugar or insulin concentration, TG, HDL, fibrinogen were significantly independent variables (Coefficients of correlation were 0.358, 0.461, 0.452, 0.349, 0.405, 0.466, 0.478, -0.433, 0.349 respectively, all p<0.05). The factors affecting IMT by multivariate regression were PCOS status and fasting insulin concentration. Conclusions: We concluded that women with PCOS might have an increased risk of subclinical atherosclerosis and insulin resistance was assumed to be the main risk factor of atherosclerosis.