The effect of dividing the sphincter of Oddi at endoscopic sphincteretomy (EST) on the filling and emptying aspects of gallbladder function has not been definitely established in humans. This prospective study is designed to examine the effects of EST on gallbladder emptying. In 13 patients (8 men and 5 women; mean age, 60.54 years +/- 2.14: range, 45-75 years), postprandial gallbladder emptying was measured ultrasonographically before and after EST (within 1-4 days). The fasting volumes after 8 hours of fasting, at times 0 min and before the test meal was given, residual volume (the smallest postprandial volume), gallbladder ejection fraction (EF), and total ejection volume, at 10, 20, 30, 40, 50, 60, 70, 80, and 90 min after the test meal, were studied. The fasting gallbladder volume and the residual volume tended to decrease after EST, but the differences were not significant (40.21 +/- 10.79 mt and 35.48 +/- 11.21 mt, 17.79 +/- 4.83 mt, and 13.10 +/- 4.83 mt, respectively; p > 0.05). Maximum EF was found to be 19.72% at 40 min and increased to 28.62% at 70 min after EST. Although the difference was not statistically relevant, a trend of improvement was evident after EST. The ejected volumes after EST have depicted a trend toward increase, without reaching to any statistical significance (p > 0.05). Our results demonstrate at least no adverse effects of EST and further support some positive effects on gallbladder kinetics.