Sialic acid residues of plasma membrane glycoproteins of rabbit corneal endothelial cells were radiolabeled by oxidation with sodium periodate and reduction with sodium borotritide. Surface-labeled glycoproteins were resolved by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. The major surface labeled glycoproteins were designated GP 1-8 in order of their increasing mobility on the gel (M.W. = 220K (GP-1), 200K (GP-2), 170K (GP-3), 135K (GP-4), 110K (GP-5), 95K (GP-6), 80K (GP-7), and 44K (GP-8). On the basis of the behavior of these glycoproteins on various carrier-bound lectins, preliminary information concerning their saccharide moieties was obtained. All 8 components bound to agarose-linked wheat germ agglutinin; GP 4-6 bound to concanavalin A and GP 6-7 bound to Ricinus communis agglutinin. No component bound to Bandeiraea simplicifolia I, Bandeiraea simplicifolia II, Ulex europeus or soybean agglutinin. These data suggest that in addition to the presence of sialic acid/N-acetylglucosamine residues in all the eight glycoproteins, oligosaccharides with terminal beta-galactose residues occur in GP-6 and GP-7 while mannose (glucose) residues occur in GP 4-6.