The postprandial release of cholecystokinin (CCK) regulates gallbladder (GB) contraction but little is known about the role, if any, of the still-elevated CCK blood levels on subsequent GB refilling. To assess the role of CCK in GB refilling, a CCK-receptor antagonist, loxiglumide, or saline were infused intravenously in a random double-blind fashion after the ingestion of a liquid test meal in 16 healthy subjects. An identical study protocol was performed in 10 GB "contractor" patient with radiolucent stones to ascertain whether the reported reduced CCK effect on GB emptying also affects GB refilling. GB volumes were assessed ultrasonographically in the fasting state and for 150 min at 15-min intervals after meal ingestion. GB volumes during postprandial refilling were significantly greater during loxiglumide than placebo infusion (P < 0.01), but they did not differ between gallstone and control subjects. In conclusion, postprandial endogenous CCK has a relevant role in delaying GB refilling, and this effect is not altered in patients with radiolucent gallstones.