Eight Japanese patients with mesenteric varices were diagnosed by angiography. All patients suffered from portal hypertension and had a history of previous abdominal surgery or peritonitis. The mesenteric varices of these patients were thought to be related to adhesion. Of the eight patients, five showed hepatic encephalopathy. None of the patients had a history of massive lower-gastrointestinal bleeding. All mesenteric varices were opacified in the portal phase of superior mesenteric arteriograms. To study the superior mesenteric artery, 50-60 ml of 76% Urografin was injected after infusion of prostaglandin E1 or F2 alpha. Regarding patients treated in the early part of the study, a vasodilator was not used and the contrast dosage was modest. In all eight patients, the mesenteric varices communicated with the systemic venous circulation through the gonadal veins. In seven cases, the mesenteric varices on the right side of the mesenteries drained into the right gonadal veins which flowed into the inferior vena cava (IVC). In the remaining case, the mesenteric varix on the left side drained into the left gonadal vein which flowed into the left renal vein. In three patients with right-sided varices, venous blood sampled from the right gonadal vein and from the distal and proximal IVC showed a high concentration of ammonia in the right gonadal vein and step-ups between distal and proximal IVC.