Gallbladder contraction and hormone release were measured in six healthy volunteers after their ingestion of two commercially available fatty meals (Biloptin Fatty Meal and Sorbitract) and intravenous bolus injection of 1 Ivy Dog Unit/kg body weight cholecystokinin (CCK) to compare the effectiveness of fatty meals to CCK. Differences in gallbladder volumes, rate constants of emptying, and times of maximal contractions, as measured by real-time sonography, were not statistically significant. Peak levels of CCK, a potent stimulant of gallbladder contraction, and of pancreatic polypeptide, an inhibitor of gallbladder contraction, were significantly higher (P less than .05-P less than .005) after administration of CCK than after ingestion of each fatty meal, but this did not significantly affect emptying rate or maximal contraction. We conclude that the use of intravenous CCK does not offer any advantage over the ingestion of fatty meals in radiographic studies of gallbladder involving induced contractions.