Background: Endoscopic papillary balloon dilation for treatment of bile duct stones is likely to preserve papillary function. However, endoscopic papillary balloon dilation may affect gallbladder motility. We investigated the effects of endoscopic papillary balloon dilation on gallbladder motility. Methods: Ten patients with an intact gallbladder (six with and four without gallbladder stones) who underwent endoscopic papillary balloon dilation for choledocholithiasis were studied. Gallbladder motility was examined before and 7 days and 1 month after endoscopic papillary balloon dilation. Gallbladder volume, while fasting and after dried egg yolk ingestion, was determined by ultrasonography. Results: Before endoscopic papillary balloon dilation, particularly in patients with gallbladder stones, the gallbladder showed significantly larger fasting volume and lower yolk-stimulated maximum contraction compared with control subjects. Seven days after endoscopic papillary balloon dilation, fasting volume was decreased and maximum contraction was increased, regardless of the presence of gallbladder stones, with significant differences from the values before endoscopic papillary balloon dilation. One month after endoscopic papillary balloon dilation, these changes were reduced and gallbladder function did not differ significantly from baseline. Conclusions: After endoscopic papillary balloon dilation, gallbladder motility improves transiently at 7 days but returns to baseline at 1 month. In terms of gallbladder motility, endoscopic papillary balloon dilation does not seem to increase the subsequent risk of acute cholecystitis. (Gastrointest Endosc 1999;50:74-8.)