Two new intravenous cholegraphic agents, iotroxate and iodoxamate, hold a lower general toxicity, lower protein binding, and claim a higher rate of biliary excretion. Both compounds proved to be equally effective in opacifying the gallbladder and the bile ducts in a double-blind clinical study comprising 400 cases. Iotroxate gave significantly earlier good or adequate visualization as a result of its higher excretion rate by the liver (P less than 0.05). Side effects were observed in fewer patients in the iotroxate group (11.6%) compared with the iodoxamate group (16.4%, P greater than 0.05). In a second double-blind study, an iotroxage group of 97 patients who received two thirds of the overall content of iodine (3.6 g) was compared with a group of 98 patients, who received ioglycamate (5.3 g). Visualization was equal in the two groups, while side effects were significantly reduced to 10.3% in the iotroxate group against 20.4% (P less than 0.05). The higher biliary clearance of iotroxate permits a reduction of the amount of iodine.