The ability of hepatic plasma membranes to bind desialylated glycoproteins as a prelude to transport and catabolism has been reported earlier. The present study describes the purification, by affinity chromatography, of an hepatic protein which retains the characteristic binding properties associated with the membranes. The isolated material, which is watersoluble and free from lipids, has been identified as a glycoprotein in which 10 % of the dry weight consists of sialic acid, galactose, mannose, and glucosamine in a molar ratio of 1:1:2:2. The integrity of the terminal sialic acid residues and the presence of calcium were shown to be absolute requirements for binding. Physical chemical studies indicated a high degree of aggregation in the final, water-soluble preparation.