Four major glycoproteins were extracted by dilute salt solution from porcine valvular tissue. Two of these major glycoproteins, porcine valve glycoprotein I and porcine valve glycoprotein III, were isolated and purified by fractionation of salt extract with ammonium sulfate followed by column chromatography on DEAE-cellulose. The purified glycoproteins appeared to be homogeneous by polyacrylamide disc electrophoresis in several buffer systems, and by Sephadex filtration. The porcine valve glycoprotein I had a MW of approximately 120,000. Isoelectric focusing yielded a single band, pI = 5.8. The glycoprotein contained large amounts of acidic amino acids, and amide nitrogen. The carbohydrate moiety was composed of fucose, mannose, galactose, glucose, glucosamine and galactosamine in the molar ratio of 5:10:15:12:7:2/mol of glycoprotein. The 2nd major glycoprotein, porcine valve glycoprotein III, had an approximate MW of 72,000. This glycoprotein gives two bands upon analytical isoelectric focusing with isoelectric points of pI = 4.1 and 4.3. Porcine valve glycoprotein III contained large amounts of acidic amino acids and low amounts of amide nitrogen. Its carbohydrate moiety was composed of glucose, galactose, mannose, fucose, glucosamine, and sialic acid in the ratio of 3:3:2:1:4:1 mol/mol of glycoprotein. This glycoprotein was similar to a glycoprotein preparation isolated from porcine aortic intima by Wagh and Roberts.