C-reactive protein (CRP) has been known to be associated with vascular inflammation and hypertension. Pulse wave velocity (PWV) increases according to the degree of the arterial stiffness in hypertension patients. Therefore, PWV may be correlated with CRP levels in treated hypertensive patients, irrespective of medication. We sought to determine whether there is a correlation between hsCRP and arterial stiffness in non-diabetic treated hypertensive patients, independent of cardiovascular risk factor. This study consisted of 424 non-diabetic patients at least 45-years-old who were being treated for hypertension. At the time of enrollment, the patients underwent a baseline laboratory assessment of C-reactive protein levels and pulse wave velocity (PWV). Heart to femoral PWV (hfPWV) and brachial to ankle PWV (baPWV) were used as a marker of arterial stiffness. Subjects were categorized according to tertiles of hsCRP level [Group 1: first tertile (0.20-0.46 mg/L), Group 2: second tertile (0.47-1.15 mg/L), Group 3: third tertile (1.17-9.71 mg/L)]. Group 1 consisted of 141 patients (mean age 58+/-8 years), Group 2 had 142 patients (mean age 60+/-9 years) and Group 3 had 141 patients (mean age 61+/-8 years). The hfPWV and baPWV increased significantly along with the hsCRP level. Group 1, Group 2 and Group 3 demonstrated hfPWV and baPWV of 965+/-199 and 1438+/-246, 975+/-174 and 1487+/-258 and 1043+/-215 and 1566+/-252 cm/s, respectively (p<0.01). The hfPWV also showed a strong correlation with baPWV (r=0.698, p<0.001). The hsCRP level was independently associated with arterial stiffness (hfPWV: R(2)=0.273, p<0.001; baPWV: R(2)=0.284, p=0.001) after controlling for age, body mass index, systolic blood pressure (BP), heart rate, gender, HDL-cholesterol, triglyceride, glucose level and medications. In conclusion, hsCRP was associated with arterial stiffness, independent of age, systolic BP, gender, heart rate, glucose, lipid profiles and medications in treated hypertension. Therefore, hsCRP could be a useful marker of arterial stiffness in treated hypertension patients and a possible target for arterial inflammation in hypertension.