To determine the incidence of common-bile-duct lesions and their relation to liver disease in cystic fibrosis, we performed hepatobiliary scanning in 50 of 61 patients with cystic fibrosis who had hepatomegaly, abnormal liver function, or both and in 31 of 92 patients with cystic fibrosis who did not have hepatomegaly or abnormal liver function. Ninety-six percent of the patients with liver disease had evidence of biliary tract obstruction, which was defined cholangiographically as a stricture of the distal common bile duct in the majority of cases. All the patients without liver disease had normal intrahepatic and common-duct excretion of tracer. Abdominal pain was significantly more common in patients with common-duct obstruction (P less than 0.001), and enlarged gallbladders occurred only in such patients. Since fasting levels of serum bile acids were elevated in nearly half these patients, irrespective of the severity of their liver disease, serum bile acids may be markers of the severity of the common-duct lesion. We conclude that strictures of the distal common bile duct are common in patients with cystic fibrosis and liver disease. This association requires further study, since surgical relief of common-duct obstruction may prevent or ameliorate the hepatic complications of cystic fibrosis.