Steatorrhea associated with advanced cirrhosis of the liver was studied by means of the I131-labeled oleic acid absorption test. The validity of the use of this test as a measure of fat absorption by the small intestine was reviewed. Malabsorption of oleic acid was demonstrated in each of the 6 cirrhotic patients examined. The impaired absorption of oleic acid was attributed to pathologic changes in the mucosa of the small intestine secondary to portal hypertension. The clinical implications of this finding were discussed. The possibility that a protein-losing enteropathy might contribute to the hypoalbuminemia of advanced cirrhosis was investigated by means of intravenously administered I131-labeled polyvinylpyrrolidone and I131-labeled serum albumin. However, no significant loss of protein through the gastrointestinal tract was demonstrated in the 4 cirrhotic patients examined for this condition.