A comparison of two oral cholecystopaques, iopanoic acid (Telepaque) and iopronic acid (Oravue), was performed using normal volunteers. Using a double-blind crossover design, comparisons were made between the degree of gallbladder opacification and the amount of iodine recovered from the gallbladder. Bile was collected via a double lumen intestinal tube before, during, and after stimulating gallbladder contraction. There were no differences between the two agents in terms of opacification or iodine concentration. Only 19% of the administered dose of either agent was recovered, and the maximum iodine concentration in bile was 10 mg I/ml. The results suggest that this technique has merit for future comparative studies of agents concentrated in the gallbladder.