In vivo and in vitro studies indicate that the rate of absorption of Telepaque from the intestine is dependent on the pH of the gastrointestinal contents. An increase in intestinal pH in animal experiments accelerates the rate of absorption of Telepaque. Consideration of solubility properties leads to the hypothesis that the rate of absorption is limited by the rate of solution of Telepaque. Impaired radiographic visualization of the normal gallbladder may result from poor intestinal absorption of Telepaque due to low pH in the gastrointestinal tract.