1. The incidence of gallstones in patients with Crohn's disease is increased compared with that in healthy control subjects. This is in part due to reduced terminal ileal bile salt absorption and consequent increased cholesterol saturation in bile. The aim of this study was to evaluate gallbladder contractility, a second important factor in the pathogenesis of gallstones, in Crohn's disease. 2. Thirty patients with Crohn's disease and no known biliary tract disease and nine healthy control subjects were studied. After an overnight fast, gallbladder volume was determined by real-time ultrasonography before and 10, 20, 30, 40, and 50 min after ingestion of a standard liquid fatty meal. 3. Compared with healthy control subjects, patients with Crohn's disease had similar fasting gallbladder volumes (control, 18.7 ± 2.3 ml; Crohn's disease, 18.2 ± 2.3 ml). Percentage emptying was significantly impaired at 30, 40 and 50 min in patients with Crohn's disease compared with control subjects. Patients with Crohn's disease limited to the small bowel had gallbladder contractility that was comparable with that of control subjects, whereas in those with large-bowel disease, minimum residual gallbladder volume was significantly smaller than in control subjects. Patients with both large- and small-bowel Crohn's disease demonstrated the most marked abnormalities, with gallbladder volumes significantly larger than those of control subjects at 30, 40 and 50 min. Likewise, patients with Crohn's disease who had undergone previous bowel resection had impaired emptying at 30, 40 and 50 min. 4. In summary, gallbladder contractility is significantly impaired in patients with Crohn's disease, an abnormality which is most marked in those patients who have undergone bowel resection or have both large- and small-bowel disease. Impaired gallbladder contractility may thus be a second factor contributing to gallstone formation in certain patients with Crohn's disease.