The polycystic ovary syndrome (PCOS) is the most common endocrine-metabolic disorder, also associated with the metabolic syndrome. Serum high sensitivity C-reactive protein (hs-CRP), a marker of low-grade chronic inflammation is a potent predictor of cardiovascular events, closely linked to metabolic syndrome features and higher in patients with PCOS. However, hs-CRP in lean patients with PCOS has not been fully evaluated and few data are available. We aimed to investigate the relation between glucose intolerance and hs-CRP levels in lean patients with PCOS, and to evaluate the possible relationship between hs-CRP and PCOS by evaluating PCOS-related metabolic abnormalities in Korean women. We consecutively recruited 115 lean (BMI < 25kg/m(2)) patients diagnosed with PCOS and 103 lean healthy controls. The PCOS group was divided two groups: impaired glucose regulation (IGR) and normal glucose tolerance group (NGT). In lean patients with PCOS, hs-CRP level was higher in the IGR group than in the NGT group (0.60 ± 1.37 versus 0.18 ± 0.46, p(Bonf) = 0.023) and other metabolic risk factors were also higher in the IGR group than in the NGT group. And there were close relationships between hs-CRP level and metabolic risk factor, such as 2 h postprandial insulin level in the lean patients with PCOS.