The aim of this study was to specify the signs and course of patients with a dilated common bile duct without obstruction. We included patients with a dilated common bile duct of more than 12 mm on endoscopic retrograde cholangiography, and we excluded patients with stones, tumor or other visible obstruction. Two hundred and seven patients (8.4 p. 100 of endoscopic retrograde cholangiography) were included. One hundred and nineteen (57.5 p. 100) had undergone cholecystectomy. Sixty-five p. 100 of patients had signs suggesting biliary tract disease, and 78 p. 100 had biological signs of cholestasis. The size of the common bile duct was not different whether the patient had been cholecystectomized (16.2 +/- 0.3 mm.M +/- SEM) or not (16.2 +/- 0.4 mm). Forty-one patients in the non cholecystectomized group had gallbladder stones. Thus, 47 of our 207 patients (23 p. 100) had neither gallbladder stones nor previous cholecystectomy. Endoscopic retrograde cholangiography was completed by endoscopic sphincterotomy in 130 patients, either in the intent of not missing obstruction, or for therapeutic purposes. Follow-up more than one month after endoscopic retrograde cholangiography was available for 159 patients (77 p. 100). The median survival was 73 months. One hundred and ten patients (69 p. 100) were asymptomatic, 36 (23 p. 100) had atypical abdominal pain while 13 (8 p. 100) patients had episodes of biliary colic and/or fever and/or jaundice. During follow-up, an initially unrecognized obstacle was discovered in 8 patients: 5 common bile duct stones, 2 ampullary tumors and one pancreatic tumor.(ABSTRACT TRUNCATED AT 250 WORDS)