In 1962, animal experiments in rabbits and pigs demonstrated that subtotal ileal bypass would lead to a marked decrease in cholesterol absorption capactiy and a sharp decline in circulating-cholesterol levels.1This induced lowering of the blood cholesterol level endured for the duration of the bypass period. Further work showed that although the entire small intestine has the capability to absorb cholesterol, greater amounts are taken up by the ileum. Too, the intestinal transit time plays a role in cholesterol absorption. Finally, it appears that the maximal circulating-cholesterol reduction obtainable by a limited intestinal bypass can best be achieved by subtotal ileal bypass with bypass including the ileocecal valve.2The finding of ileal preference in cholesterol absorption corroborates the earlier results of Byers and associates.3Our analysis, by statistical comparison of age and sex matched populations of human controls with patients who had undergone ileal resections for causes