Blood flow directions of the portal trunk, splenic vein, and superior mesenteric vein were studied using an ultrasonic Doppler duplex system in 146 healthy adults, 132 patients with liver cirrhosis, 76 with hepatocellular carcinoma, 32 with idiopathic portal hypertension, 134 with chronic hepatitis, 18 with acute hepatitis, and 142 with other diseases. Spontaneous hepatofugal flow in one or more of the three vessels examined was detected in 14 patients. Spontaneous hepatofugal flow in the portal trunk was detected in three patients with liver cirrhosis. In two of these three patients, the hepatofugal flow in the portal trunk disappeared after medication. This is interesting, since hepatofugal flow may, in fact, be more common than we suspected in patients who, because of the severity of their disease, are not able to undergo invasive examination. Postoperative hepatofugal flow in the portal system was detected in 20 of 71 cases: 15/17 patients after interposition mesocaval shunting, 2/17 after distal splenorenal shunting, 2/31 after splenectomy, and 1/6 after splenic artery occlusion with steel coils. In more than half the cases of interposition mesocaval shunting (9/17 patients), blood flow in the portal trunk was hepatofugal. However, hepatopetal blood flow in the portal trunk was maintained in most cases of distal splenorenal shunting (13/17), showing the merits of this technique as a selective portosystemic shunt operation.