Objectives: It has been shown that serum uric acid (SUA) constitutes an important independent risk factor for cardiovascular disease. We investigated SUA levels in patients with coronary artery ectasia (CAE). Study design: Serum uric acid levels were measured in three groups of patients who underwent coronary angiography. One group consisted of 97 consecutive patients (69 males, 28 females; mean age 58.1±9.5 years) with isolated CAE, another group included 104 patients (79 males, 25 females; mean age 58.4±8.8 years) with coronary artery disease (CAD), and finally 90 subjects (66 males, 24 females; mean age 57.6±10.1 years) with normal coronary arteries comprised the control group. Coronary artery ectasia was defined as a luminal dilatation of at least 1.5 times of the adjacent normal coronary segments, without any stenotic lesions. In addition, patients with CAE were assessed in four groups of severity and extension. Results: The three groups were similar with respect to age, sex, body mass index, and the frequencies of hypertension, diabetes mellitus, and smoking (p>0.05). The mean SUA level did not differ significantly between the CAE and CAD groups (6.6±1.9 mg/dl and 6.3±1.9 mg/dl, respectively; p=0.184); however, compared with the control group (5.4±1.8 mg/dl), SUA levels were significantly higher in both groups (p<0.001). A significant correlation was found between the SUA level and the presence of isolated CAE (r=0.625; p<0.001). Multivariate logistic regression analysis showed an independent relationship between isolated CAE and SUA (OR 1.896; 95% CI 1.1048-1.5014; p<0.001). Serum uric acid levels did not differ significantly among the four subgroups of CAE severity. Conclusion: Our study is the first to demonstrate significantly increased SUA levels in patients with isolated CAE. Our results support relevant data suggesting an association between endothelial function and the SUA level.