The aim of this study was to determine the effect of Billroth II gastric resection (BII) without vagotomy on gallbladder contraction in response to meal and CCK-OP infusion. Fourteen duodenal ulcer patients were studied before surgery and six months postoperatively. Gallbladder volume was measured by real-time ultrasonography. After surgery, there was a significant increase in fasting gallbladder volume (P < 0.05). Postprandial gallbladder emptying was not significantly affected by gastrectomy apart from a trend towards a shorter t1/2 and a larger ejection volume. In addition, postoperative gallbladder relaxation was more pronounced at time 120 min. In response to cholecystokinin-octapeptide (CCK-OP) infusion, there was a significant decrease of t1/2 after BII and a prolonged contraction with a significantly reduced gallbladder volume. Our data show that the gallbladder response both to meal and CCK-OP infusion is modified after BII and a larger postoperative gallbladder volume may play a role in the pathogenesis of gallstone disease after gastric surgery.