1. The absorption of physiological doses of tritiated α-tocopherol has been studied in seven control subjects and in twenty-three patients with malabsorption due to various causes.
2. Control subjects absorbed between 55·0 and 78·6% of an oral dose. Radioactivity appeared in the plasma between 1 and 3 hr, reached a peak between 5 and 9 hr, and subsequently fell exponentially with a mean half-life of 53 hr. Radioactivity in plasma was almost all associated with free α-tocopherol.
3. Absorption of α-tocopherol was most severely impaired in patients with biliary obstruction, and somewhat less severely impaired in patients with exocrine pancreatic insufficiency. Malabsorption in patients with an abnormal small intestinal mucosa varied with the severity of the condition, and could be correlated with the degree of steatorrhoea.
4. In two patients with intestinal lymphangiectasia, malabsorption of the vitamin was relatively more severe than that of fat. Mild malabsorption was found in five of the six patients who had had a partial gastrectomy.
5. The amount of radioactivity recovered from the urine in 3 days ranged from 0·0 to 21·4% of the dose given and could be correlated with the degree of absorption.