Background/Aims: A positive correlation has been clearly demonstrated between juxtapapillary duodenal diverticulum(JPDD) and cholelithiasis. However, it is stil] unknown whether there is a causal relationship between JPDD and biliary calculi. The possibility is that JPDD may interfere with the function of the sphincter of Oddi(SO). The disturbance of the fuction of SO is currently thought to predispose to gallstone formation, especially in the common bile duct(CBD). However, some controversial results were reported about the SO dysfunction in patients with JPDD. In the present study the SO function of cholelithiasis patients with and without JPDD was examined to clarify the clinical role of JPDD in the formation of gallstones. Methods: We performed the manometry of the SO in 27 patients with JPDD and 20 patients without JPDD. After cannulation into the common bile duct(CBD), pressure measurements were made across the SO for 3 minutes with incremental withdrawals of the catheter pausing l minute or longer at each station. Results: Basal pressure and amplitude of the phasic contraction of the SO in patients with JPDD were signi- ficantly lower than the values in patients without JPDD(p:0.05). In case of patients with CBD .tones the hasal pre.isure and amplitude of the phasic contraction of the SO was significantly lower in those with JPDD than those without JPDD(p-- 0.05). In patients with cholecystolithiasis, hov:ever, there was no significant difference in the SO function between those with and without JPDD. There was no statistica1 correlation between the type of JPDD and SO function. ('onclusions: This finding indicates that there is a dysfunction of the SO in patients with JPDD. This may he partly responsible. For the high incidence of biliary calculi in patients with JPDD. (Korean J Gastroenterol 1995;27: 412-422)