The accuracy and reliability of a balloon catheter for measuring wedged hepatic venous pressure (WHVP) were evaluated in 82 simultaneous determinations using the balloon catheter technique and the direct measurement of portal venous pressure. These measurements showed a close positive correlation (r = 0.97) over a wide range of pressures in 12 normal and 4 cirrhotic dogs. Studies were then performed in 13 cirrhotic patients in whom the balloon catheter was introduced using the Seldinger technique. Free hepatic venous pressure (FHVP) was measured with the balloon undistended. By distending the balloon to occlude the hepatic vein, the WHVP was recorded. Comparison of FHVP and WHVP with the conventional and balloon techniques revealed a close positive correlation (r = 0.89 and 0.93, respectively). The correlation was virtually perfect for the hepatic venous pressure gradient (WHVP-FHVP, r = 0.98). The balloon technique offers many advantages over the conventional approach, including the ease of achieving and demonstrating the wedged position from the femoral approach, the ability to measure the free and wedged pressure repeatedly without manipulating the catheter, and the measurement of pressure in a larger, more representative segment of the liver.