The effect of bilirubin on biliary and renal excretion of methylglucamine-iodipamide at an infusion rate of 1.3, 2.6 and 5.2 mu mol/min/kg was studied by intravenous injection into five dogs with normal liver functions and chronic duodenal fistulas. Unconjugated bilirubin administered in a dose of 0.1 mu mol/min/kg reduced biliary iodipamide excretion and concentration significantly, but did not affect renal contrast material excretion. This indicates that the unsatisficatory radiological results of intravenous cholangiography in hepatic and obstructive jaundice depend not only on the reduced excretion capacity of the liver, but are also due to a direct inhibitory effect of bilirubin on biliary contrast material excretion. In the presence of hyperbilirubinaemia, the highest iodine concentrations in the bile were obtained with the highest iodipamide serum levels; a reduction in contrast material dose or prolongation of the period of contrast material infusion therefore does not appear to be indicated in jaundiced patients.