The prevalence and the pathogenesis of gallstones in patients with chronic pancreatitis have never been studied prospectively. The aim of this study was to evaluate prospectively the prevalence of gallstones with ultrasonography and to look for markers of pigment or cholesterol stone formation in gallbladder bile. Ultrasonography was performed in 39 patients and detected gallstones in 7 patients and sludge in 3. Common bile duct and intrahepatic bile duct dilatation were observed in 16 and 13 patients, respectively. Liver biopsies were obtained in 31 patients and cirrhosis was found in 4. There were calcium bilirubinate granules in 7 of the 27 bile samples examined. Cholesterol crystals were not found in any case. The nucleation time (median: 21 days) was higher in patients with chronic pancreatitis than in patients with cholesterol stones (median: 2 days) (P < 0.001) but was not different from nucleation time in patients either free of stones (median: 21 days) or with pigment stones (median: 21 days). The cholesterol saturation index was similar in patients with chronic pancreatitis and in controls. The 2 patients with chronic pancreatitis who underwent cholecystectomy had pigment stones. Calcium bilirubinate granules were more frequent in patients with intrahepatic bile ducts dilatation (P < 0.02). In conclusion, this study demonstrates a high prevalence of cholelithiasis in chronic pancreatitis patients. Pigment stone formation could be favored by cholestasis.