The relationship between peripapillary duodenal diverticulum and benign biliary tract disease was studied. Peripapillary duodenal diverticulum could be classified pathophysiologically into three types. Type I represents the disease not directly affecting the biliary tract. Type II shows the elevation of bile duct pressure directly caused by intraduodenal pressure loading. Type III includes patients in whom the diverticulum is small and is prone to cause papillitis or mechanical stimulation. This, then, may lead to organic changes in Oddi's sphincter and possibly to biliary tract disorders. In our patients, many cases of peripapillary duodenal diverticulum were associated with calcium bilirubinate stones, indicating that a peripapillary duodenal diverticulum is likely to lead to bile stagnation and ascending infection of the biliary tract and thus cause formation of calcium bilirubinate stones. Based on findings in this study, we want to emphasize that Type II peripapillary duodenal diverticulum should be surgically treated.