Portacaval and mesocaval interposition shunts using vascular prosthetic grafts were compared in 37 cirrhotic patients without portal vein thrombosis who were operated on for previous or active variceal hemorrhage. Operative indications and severity of liver disease were similar in the two groups of patients having one or the other procedure. The major difference in results was that none of the 23 patients with portacaval H-graft shunts had rebleeding, while 4 of 14 had rebleeding from varices after mesocaval interposition shunting. This contributed to the higher operative mortality associated with the latter procedure. The index of operative difficulty, as judged by blood loss and length of operation, and postshunt encephalopathy rates were similar for both procedures. Thus, while the mesocaval interposition shunt offers none of the reported theoretical advantages over portacaval H-graft shunt, it does place patients at greater risk of postoperative variceal rehemorrhage. It is concluded that the portacaval interposition shunt, because of its effectiveness and technical expediency, may be the operation of choice in cirrhotic patients with bleeding varices who are not otherwise candidates for other procedures which reduce portal flow less drastically.