The objective of this study was to characterize the effect of proglumide, a cholecystokinin (CCK) antagonist, on gallbladder contraction stimulated by CCK in conscious dogs. The gallbladder contraction was monitored by a strain-gauge force transducer that was chronically sutured onto the serosal surface of the gallbladder. The results of this study show that proglumide, given as an intravenous bolus (2.5, 5, 10, 20, and 40 mg/kg) or as a continuous intravenous infusion (150 or 300 mg/kg/h, 10 min), can block the stimulatory action of CCK in a dose-related manner. Bolus administration of proglumide resulted in a transient inhibition, whereas continuous infusion of proglumide resulted in a prolonged antagonism of CCK-stimulated gallbladder contraction. Review of the data leads to the conclusion that the antagonistic action of intravenously administered proglumide on CCK-stimulated gallbladder contraction may be characterized as rapid and reversible.