Purpose Bile duct dilatation after cholecystectomy continues to be a matter of controversy. We aimed determine the magnitude of common bile duct (CBD) dilatation after cholecystectomy followed up to 1 year. Methods Sixty-four cases (age, 47.3 ± 11.7 years; men, 28; women, 36) enrolled in this study. They received laparoscopic cholecystectomy in Chungbuk National University Hospital for symptomatic cholelithiasis or gallbladder polyps with normal bile duct, less than 7 mm. The CBD diameter was measured by one radiologist using ultrasonography at the maximum point after full length evaluation of extrahepatic bile duct. Forty-five and thirty-one cases were followed at 6 months and 1 year, respectively. Results The CBD was dilated slightly from 4.1 mm at baseline to 5.1 mm at 6 months and 6.1 mm at 12 months after cholecystectomy. The number of cases of CBD dilatation of more than 7 mm at 6 months and at 12 months after cholecystectomy were 11 (24.4%) and 9 (29.0%), respectively. Seven cases at 6 months and 5 cases at 12 months showed bile duct dilation of more than 3 mm compared to baseline. There were no cases having bile duct dilation of more than 10 mm. Conclusion Postcholecystectomy dilatation of the bile duct occured slightly in most cases. But some cases showed more than 3 mm dilatation over baseline. Asymptomatic bile duct dilatation of up to 10 mm can be considered as normal range in patients after cholecystectomy.