Complex saccharides were extracted with 0.9% NaCl at 0 degrees C from rabbit small intestine, then fractionated with cetylpryridinium chloride (CPC), followed by DEAE-Sephadex A-25 column chromatography and by GEON-zone electrophoresis. An acidic glycoprotein (Fr. A-1) thus obtained was shown to be homogeneous by electrophoreses on cellulose acetate membrane and on sodium dodecyl sulfate (SDS)-polyacrylamide gel, as well as by gel filtration on Sepharose 4B. It contained 40.0% protein, 52.7% carbohydrate, and 1.6% sulfate. The principal sugars in the sulfated glycoprotein were galactose, glucosamine, galactosamine, and sialic acid. Small quantities of mannose, L-fucose, and glucose were also present. Glutamic acid, threonine, aspartic acid, alanine, serine, leucine, proline, glycine, valine, and histidine were the major amino acids of the protein moiety. Small amounts of other basic amino acids, sulfur-containing amino acids and aromatic amino acids were also present.