Diatrizoate, iopamidol and ioxaglate were compared in five normal dogs and in five dogs with presinusoidal cirrhosis and portal hypertension for arterial portography. After selective injection of 40 ml of each contrast agent in iodine concentrations of 320 mg per ml into the superior mesenteric artery, portal vein blood samples were collected in 2-second intervals and the iodine concentrations determined using x-ray energy spectrometry. The highest iodine concentrations in the portal blood were found in both normal portal pressure and portal hypertension with ioxaglate, followed by iopamidol and diatrizoate in this order. Compared with diatrizoate, ioxaglate and iopamidol increased the peak portal blood iodine concentrations 45% and 22%, respectively. The use of ioxaglate in arterial portography should show the portal system at least as well as when a conventional contrast agent is used together with a vasodilator such as tolazoline.