Background: Opium and its derivatives are widely abused throughout the world. Recent case reports and a few limited studies have suggested that opiates cause dilation of the common bile duct of the abusers. Material/Methods: Our case-control study, lasting 7.5 months, investigated 121 male adult addicts and 142 nonaddicted controls for biliary tract diameters, using ultrasonography. The study was conducted in Bahonar Hospital in Kerman. Neither the addiction cases nor the non-addict controls revealed any hepatobiliary tract symptoms. The subjects were asked to fill in a questionnaire. After the exclusion of the symptomatic cases, ultrasound examinations were carried out and the findings from questionnaires and US examinations were recorded. Results: The mean ±SD diameter of the common bile duct was 4.78±2.58 for addicts and 3.37±2.25 for non-addicts. CBD wall thickness was 1.969±0.61 mm in addicts versus 1.73±0.631 in non-addicts. The differences were statistically significant. According to the multivariate analysis, the duration of opium abuse was a significant factor. Conclusions: We concluded that CBD dilation and increased CBD wall thickness can be expected in people with a prolonged history of opiate addiction.