The technique of percutaneous transhepatic portal vein cannulation provides a valuable means for determining portal pressure, direction of blood flow, and visualization of the entire portal system in the nonanesthetized patient. This technique, along with selective celiac arterial, superior mesenteric arterial, and renal venous catheterization, was used in the evaluation of a series of 17 splenorenal venous shunts [eight nonselective and nine selective (modified) distal splenorenal shunts]. As a result of these studies it is concluded that (1) prograde portal flow is maintained in the majority of patients following nonselective or selective (modified) distal splenorenal shunts; (2) bidirectional flow occurs in various branches of the portal system before and after splenorenal shunts; (3) a significant drop in portal pressure occurs following the establishment of either type of shunt; and (4) esophageal varices are decompressed by the trans-splenic route following either type of procedure used in this study.