Background: The importance of monocyte count-to-HDL-cholesterol ratio (MHR) in cardio-vascular diseases has been shown in various studies. Ascending aortic dilatation (AAD) is a common complication in the patients with bicuspid aortic valve. In this study, we aimed to investigate the relationship between MHR and the presence of aortic dilatation in the patients with bicuspid aortic valve. Methods: The study population included totally 347 patients with bicuspid aortic valve.169 patients with aortic dilatation (ascending aorta diameter >= 4.0 cm) and 178 patients with no aortic dilatation. Echocardiographic and laboratory measurement was done and compared between groups. Results: The mean age of the participants was 44.7 +/- 15.4 years and average ascending aorta diameter was 3.2 +/- 0.3 cm in dilatation negative group and 4.4 +/- 0.4 cm in positive group. MHR was significantly increased in in patients with aortic dilatation. MHR and uric acid level was independently associated with the presence of aortic dilatation in the patients with bicuspid aortic valve. Conclusion: We found a significant relationship between MHR and aortic dilatation in the patients with bicuspid aortic valve.