There is an increased incidence of gallstones in patients who have undergone Billroth II (BII) gastrectomy for duodenal ulcer. To explore the mechanisms underlying this, we examined changes in gallbladder volume induced by a meal and by intravenous administration of cerulein, in 13 BII patients and in 13 normal subjects. Gallbladder volume was measured by real-time ultrasonography. In the fasting state, gallbladder volumes were significantly larger in BII patients than in controls. The percent decrease in gallbladder volume after the meal was significantly less and maximum volume reduction observed throughout the study occurred sooner in BII patients than in controls. In contrast, the kinetics and magnitude of the reduction in gallbladder volume induced by cerulein were similar in the two groups. These findings suggest that the altered gallbladder response to a meal is due to impaired postprandial stimulation of gallbladder following BII gastrojejunostomy.