Background and Objective: There is evidence of association between aging and increase in the normal limit of the common bile duct (CBD) diameter. As aging is a documented risk factor for atherosclerosis, and the possible effect that atherosclerosis can have on the CBD diameter via affecting its smooth muscle contractility and blood flow, we decided to determine the association between CBD diameter and atherosclerosis in the abdominal aorta quantified by Agatston score. Methods: A total of 99 asymptomatic patients (53 males and 46 females; age range of 18 to 88 years) without history of cholecystectomy who underwent abdominal contrast-enhanced CT scan were included. The CBD diameter was calculated. The atherosclerosis of the abdominal aorta was quantified by Agatston score. Results: Mean (±SD) CBD diameter was 6.14 (±1.95) mm; range= 2.4 to 12.7 mm. Agatston score was 0 in 59 patients. In the remaining 40 patients, median (interquartile range, IQR) Agatston score was 497.5 (2026.3). Mean (±SD) CBD diameter in patients with Agatston score > 0 was 7.39 (±2.07) mm compared to 5.29 (±1.32) mm in patients without calcification plaque (P< 0.001). A moderate correlation was seen between CBD diameter and Agatston score (ρ= 0.43; P= 0.005). Conclusion: Atherosclerosis of the aorta as measured by Agatston score showed a significant moderate correlation with CBD diameter. Although the exact cause of increased CBD diameter with advancing age is not understood, a general atherosclerotic process which occurs with aging may affect smooth muscle of the CBD. Whether an upper limit for normal CBD should be defined or not when evaluating dilated CBD for patients with subclinical or clinical atherosclerosis needs further studies.