A fatty meal is a potent stimulator of cholecystikinin (CCK) in human body. The biological effect of CCK is increasing bile secretion and relaxing the sphincter of Oddi. Theoretically, a fatty meal should facilitate the effect on cannulation at ERCP. If a fatty meal can make the major papilla cannulation easier, it may significantly shorten the procedure time for ERCP and even decrease complications of the procedure, since the complication rate of post-ERCP is positively related to the time of the procedure.