Using transrectal portal scintigraphy with I123 iodoamphetamine, we calculated the portosystemic shunt index and investigated the portal hemodynamics in patients with various liver diseases. The shunt index tended to increase in the order of chronic hepatitis, primary biliary cirrhosis, compensated liver cirrhosis, and decompensated liver cirrhosis. An increase in the stage of esophageal varices (assessed endoscopically) also tended to be associated with an increase in the shunt index. The shunt index correlated significantly with both the ICG test and the spleen index. Accordingly, measurement of the shunt index by this method appeared to accurately reflect the existence and severity of portosystemic shunting, and to be of value in the evaluation of portal circulatory abnormalities. However, no clear differences were found in the shunt index following hepatic arterial injection chemotherapy for hepatocellular carcinoma, or endoscopic injection sclerotherapy for esophageal varices.