Gallbladder stasis during prolonged total parenteral nutrition (TPN) has been documented. We have examined the effect of intravenous amino acid infusion on human gallbladder contraction and release of cholecystokinin (CCK). Five healthy adult volunteers were given amino acid infusions at different rates (65, 125, 240, and 600 mg.kg-1.h-1). The volume of the gallbladder was calculated by means of ultrasonographic measurements. Plasma samples were analyzed for CCK immunoreactivity. Gallbladder and hormone responses after intravenous amino acids were compared with responses after a fat meal, after a protein meal, and after ingestion of an oral amino acid mixture. We found that intravenous amino acids stimulated human gallbladder contraction in a dose-related manner. The mechanism of stimulation may be through the release of CCK although significant correlation was not demonstrated. The magnitude of response is similar to that seen after meal stimulation. To compare the delivery of amino acids during a standard meal and during each dose of intravenous amino acids, peripheral plasma levels of dietary amino acids were measured after a standard commercially prepared enteral supplement meal and after each dose of intravenous amino acids. Our lower doses of amino acid infused resulted in levels of circulating amino acid comparable to those after a meal. The induction of gallbladder contraction and release of CCK in human recipients of parenteral nutrition may be of value in some circumstances.