In order to determine a possible relationship between portal hypertension and the plasma volume, measurements were made in 10 patients with cirrhosis. The majority exhibited an increased plasma vol., 7 or 10 having values greater than 10% above the predicted normal. The rise was in association with evidence of portal hypertension and collateral venous circulation, was unrelated to the degree of liver enlargement or extent of liver damage. With the additional finding of an increased plasma volume in a patient with obstruction of the inferior vena cava, it was suggested that distention behind the point of portal obstruction and the increased size of the collateral vascular bed were the chief factors responsible.