Etiology of acute pancreatitis has important implications in the treatment of the disease as gallstones pancreatitis requires the correction of the underlying biliary disease. The usefulness of ultrasonography in the detection of stones in emergency has been questioned, and HIDA biliscintigraphy has been reported to be a possible indicator of biliary pancreatitis. This study compares the value of HIDA colesscintigraphy and ultrasonography in the etiologic diagnosis of 35 patients admitted and treated for acute pancreatitis in our Institution. All patients underwent ERCP for the confirmation of the findings. Cholescintigraphy showed no visualisation of the gallbladder, suggesting biliary tract stones, in 25 patients. In all of them ERCP confirmed the presence of gallbladder and/or common bile duct stones, and endoscopic sphincterotomy and later elective cholescystectomy was performed. Ultrasonography failed to demonstrate biliary stones in 11 of those patients. HIDA cholescintigraphy showed a sensitivity and a negative predictive value of 1 vs 0.56 and 0.45 for ultrasonography. From the results of our study it can be concluded that HIDA biliscintigraphy is more reliable than ultrasonography in the discrimination of biliary vs non-biliary acute pancreatitis in emergency.