PURPOSE: To evaluate common duct (CD) dilation by computed tomography (CT) in patients with intact gallbladders and diameter change over time in remote and interval cholecystectomy patients, frequency of visualization of the CD, and its relationship to age. METHODS: This IRB-approved retrospective study evaluated baseline CD diameter, intrahepatic biliary dilation, and interval duct diameter change in patients with CTs ≥ 2 years apart (n = 324), in block-randomized order by two blinded board-certified radiologists. 272 patients were divided into three groups: (1) prior cholecystectomy before the first CT, (2) cholecystectomy between the first and last CTs, and (3) no cholecystectomy. A subset of 191 nonoperated patients was evaluated for age-related dilation. RESULTS: Group 1 ducts were significantly larger than the other groups at both baseline and follow-up CTs (p < 0.001). Group 2 showed a greater increase in duct size than the other groups at follow-up (p < 0.001). The CD was measurable in 89% of the CT studies. In nonoperated patients, there was a statistically significant correlation between CD size and increasing age (p < 0.001), although the CD size remained within normal size limits. CONCLUSION: Remote cholecystectomy patients have larger CD diameters than the nonoperated and interval cholecystectomy groups. Greater increase in ductal diameter occurred between studies in the interval cholecystectomy patients, suggesting that dilation occurs after cholecystectomy. Also, the CD dilates slightly with age in nonoperated patients.