Abstract Background: Measurement of transverse diameter of the Common Bile Duct (CBD) was performed in several studies by Ultrasonography (US) and magnetic resonance imaging using Magnetic Resonance Cholangiopancreatography (MRCP). The size of the extrahepatic bile duct increases with age which should be taken into consideration by the surgeons during the surgery of the gallbladder, pancreas and duodenum. US plays a crucial role in the initial imaging work-up of a patient with jaundice. Because a dilated extrahepatic duct distinguishes obstructive from non-obstructive causes of jaundice. The size of the bile duct is considered to increase normally with age as proved by various studies especially MRCP which is more accurate than US. Aim of Study: The aim of the present work is to demon-strate anatomical variation concerning assessment of transverse diameter of CBD both in adult and geriatric age groups without biliary or hepatic manifestations and detection of age related changes in CBD as one of the causes of non obstructive biliiary dilatation. Material and Methods: The patients were divided into three groups according to their age: 1- Group I: 21-40 years. 2- Group II: 41-60 years, 3- Group III: Over 60 years. Ultra-sound and MRCP techniques were used in this study to assess the diameter of CBD in different age groups. Results: Group I: In US: In this age group the mean of the widest transverse diameter of extrahepatic bile duct was 0.25 with a range: 0.18-0.41. In males the mean was: 0.23 with a range: 0.19-0.26. In females: The mean was: 0.28 with a range: 0.18-0.41. In MRCP: In this age group the mean of the widest transverse diameter of extrahepatic bile duct was 37.5 with a range: 21-49. In males: The mean was: 36 with a range: 21-46. In females: The mean was: 40 with a range: 0.29-49. Group II: In US: The mean of the widest transverse diameter of extrahepatic bile duct was 0.32 with a range: 0.19-0.41. In males: The mean was: 0.31 with a range: 0.19- 0.39. In females: The mean was: 0.33 with a range: 0.27-0.41. In MRCP: The mean of the widest transverse diameter of extrahepatic bile duct was 46.5 with a range: 24-62. In males: The mean was: 52.6 with a range: 41-62. In females: The mean was: 40.4 with a range: 0.24-51. Group III: In US: The mean of the widest transverse diameter of extrahepatic bile duct was 0.40 with a range: 0.26-0.63. In males: The mean was: 0.39 with a range: 0.28-0.52. In females: The mean was: 0.42 with a range: 0.26-0.63. In MRCP: The mean of the widest transverse diameter of extrahepatic bile duct was 88.31 with a range: 49-180. In males: The mean was: 94.27 with a range: 69-170. In females: The mean was: 81.93 with a range: 49-180. Conclusion: Both US and MRCP modalities revealed that the widest transverse diameter of CBD increases with age.