This report is prompted (as part of continuing studies on the problem of portal hypertension) by recognition of the need for basic information on the interpretation of portograms in the living subject. This need was satisfied in part by data obtained in a previous postmortem study of the roentgen anatomy of the normal portal venous system (Doehner et al., 1955) permitting the identification of normal vessels and evaluation of normal variations in their diameter. Other features, such as collateral channels, remained a problem. A similar investigation was therefore undertaken of the abnormal portal system. This series comprises a total of 40 cases, including 34 of cirrhosis of some type: 26 cases of Laennec's cirrhosis, 2 of Laennec's cirrhosis with liver metastasis, 1 of Laennec's cirrhosis with hemochromatosis, 1 of cirrhosis with schistosomiasis, 2 of biliary cirrhosis, 1 of biliary cirrhosis with metastasis, and 1 of congestive cirrhosis (on cardiac basis). Two cases of congested liver and 4 of metastatic tumor without cirrhosis complete the number. The technic used was identical with that employed in the previous postmortem study of the normal portal venous system, cited above. Briefly, it consists of injection of a barium sulfate suspension after cannulization of a branch of the superior or inferior mesenteric vein at necropsy. Stereoradiographs of the abdomen are then obtained, and subsequently, at evisceration, an attempt is made to identify and trace the individual pathological findings revealed in the radiographs. It will be recalled that in postmortem portography the opaque medium spreads in all directions, filling all patent vessels, while in portography of the living subject, the medium follows the direction of blood flow. The greater part of this study is concerned with the pathological vascular changes encountered in Laennec's cirrhosis of the liver, in which an intrahepatic obstruction to portal blood flow is present. Certain cases, however, showing chronic passive congestion or metastatic cancer without cirrhosis, revealed a pathological collateral circulation apparently identical with that encountered in Laennec's biliary cirrhosis. Since the same general mechanism of obstruction would appear to be in operation in these cases, they have also been included. Collateral Veins and Systems in the Presence of Obstruction of the Intrahepatic Block Type Transhepatic Collaterals: Transhepatic collaterals were seen in 9 of the 40 cases. In 4 the collateral vessel arose from the left main portal branch, and in 5 from a small peripheral intrahepatic branch of the portal vein. These collaterals may communicate with the coronary vein, the vertebral plexus, or the inferior vena cava. Communications with the hemiazygos vein were also observed.