['To evaluate the effect of selective blockade of type B cholecystokinin receptors on gall bladder contraction in normal humans and to compare methods for quantitative analysis of gall bladder contraction.', 'L-365,260, a novel, nonpeptide cholecystokinin antagonist shown to be selective for type B cholecystokinin receptors, was administered every 6 h over a 5-7 day period. Plasma levels of L-365,260 were determined by high pressure liquid chromatography. Gallbladder contraction after a standardized fatty meal was measured by ultrasonography, and results were calculated by ellipsoid or sum of cylinders methods.', 'L-365,260 levels were comparable to levels in earlier studies demonstrating inhibition of pentagastrin-stimulated acid secretion in normal subjects and blockade of anxiogenic effects of cholecystokinin injections in patients with panic disorder. Regardless of the method used for estimating gallbladder size, none of the L-365,260 doses studied inhibited gallbladder contraction. Gallbladder size was most consistently estimated by the ellipsoid method using measurements normalized to individual values for minimum and maximum gallbladder dimensions.'] Does selective blockade of cholecystokinin type B receptors with L-365,260 impair gallbladder contraction in normal humans?