The atheromas of adult aortas have been found to be composed mostly of tabular crystals of a highly insoluble cholesterol-cholestanol-water adduct designated C-C-2W. Early feeding of cholestanol risks precipitation of C-C-2W on the incomplete membranes of infants. Resultant impairment of cell permeability and reactivity can give rise to incipient atherosclerosis. The pathological condition becomes patent only with adulthood, when the aorta intima-media will be stacked with the adduct and fatty streaks will occur. Cholesterol, as provided by the usual dietary sources, contains from 3 to 10% of cholestanol, quantities more than sufficient to reach the solubility product of C-C-2W: 10(-7) mg/ml. It follows that much atherosclerosis could be avoided if cholestanol-containing foods, specifically dietary cholesterol, were not fed to infants or children. Cholestanolosis and hypercholestanolemia are new concepts to be considered in dietary approaches to control of atherosclerosis.