Total plasma lipoproteins were labeled with radioactive cholesteryl ester or cholesteryl ether by transfer of these lipids from phosphatidylcholine vesicles in the presence of plasma lipid transfer activity. Intravenous injection of these preparations into hypercholesterolemic rabbits showed disappearance curves identical to those of in vivo labeled lipoproteins. Disappearance of cholesteryl ester and ether were similar during the first 24 hours, but they diverged at later time intervals, indicating recirculation of labeled cholesteryl ester. Lipoproteins labeled with cholesteryl ether were injected at 25 days, 7 days and 1 day before sacrifice of the rabbits. The maximal loss of labeled ether from the aortas during a 24-hour period ranged from 1.6% to 8.9% of the labeled ether taken up from plasma. Hydrolysis of cholesteryl ester by the artery during 24 hours averaged 35% of the calculated cholesteryl ester influx. After hydrolysis, cholesteryl ester fatty acid appeared to be esterified more rapidly than the cholesterol moiety of the cholesteryl ester.