Experiments were done to test the hypothesis that emptying the gallbladder prior to intravenous cholangiography (IVC) would result in earler and better opacification of the gallbladder. Five dogs were studied on two separate days in a crossover experiment. Each dog had a standard IVC (15-minute infusion of meglumine iodipamide) 2.5 cc/kg of following a 14-16-hour fasting period. On one of the days, 0.3 mcg/kg of Ceruletide was intramuscularly administered to each dog 30 to 45 minutes prior to the iodipamide infusion. Films obtained at the end of infusion and at 20, 40, 60, and 90 minutes were evaluated independently by three radiologists. The results indicate that pretreatment with Ceruletide produces a significant (p less than 0.05) improvement in the quality of gallbladder opacification during the first 90 minutes following iodipamide infusion. We conclude that earlier and better opacification of the gallbladder during IVC can be obtained by prior emptying of the gallbladder with a cholecystokinetic agent.