Iodoxamic acid is a new hexaiodinated cholegraphic contrast agent. The methylglucamine salts of iodoxamate and iodipamide were administered to labrador dogs as an intravenous infusion. Bile salts were also infused. The biliary concentration and output of the two agents were compared. Bile flow rate, bile salt concentration and bile salt output with the two agents were also compared. The biliary output of iodoxamate (0.70-0.78 mumol/min/kg) was more than 50% higher than the iodipamide output (0.46 mumol/min/kg). Bile salt output and concentration with iodoxamate infusion were lower than with iodipamide infusion. The bile flow rate was higher with the new agent. The complementary effects of increased contrast output and decreased bile salt output with the new agent led to a significantly higher biliary iodine concentration compared with iodipamide. The results of this study support the suggestion that iodoxamate represents a significant advance in the cholegraphic contrast media field.