Abstract Three groups of 18 rabbits were killed, 0, 16 and 32 weeks respectively after they had been fed a cholesterol-enriched diet for 8 weeks. [ 3H] Cholesterol was injected intravenously 3 weeks before addition of cholesterol to the diet was discontinued. [ 14C] Cholesterol was injected 11 weeks after the addition of cholesterol to the diet had ceased. A number of the cholesterol-fed and the previously-cholesterol-fed rabbits were injected with labeled cholesterol 3 days before they were killed. Cholesterol content and radioactivity in inner aorta, liver and serum samples were measured. A timelag of several months was observed between the concentration maxima of cholesterol in inner aorta and serum/liver. Over a period of 16 weeks of normocholesterolemia no significant reduction in aortic cholesterol concentration was seen in the rabbits previously fed a cholesterol-enriched diet. The wet weight of inner aorta and the total amount of cholesterol in the inner aorta were found to be closely correlated. The isotopic equilibration between liver and serum cholesterol took several months; during this period, no equilibration was obtained between serum and inner aorta. The 3-day influx of cholesterol from serum into inner aorta did not decrease proportionally with the concentration of serum cholesterol. During the last norm ocholesterolemic period a reduction of the total activity of previously injected labeled cholesterol was observed. This suggested that not all the cholesterol — accumulated in the aorta during and after feeding a cholesterol-enriched diet — comprised an inert cholesterol pool.