The isolation of the principal glycoprotein from human gall bladder bile samples using gel chromatography, the determination of its carbohydrate, amino acid composition and sulphate content is described. The carbohydrate composition showed a basic structure common to all glycoproteins isolated. The carbohydrate side chains consisted of a galactosamine-galactose unit and a varying number of glucosamine-galactose units. The investigated glycoproteins were divisible into groups with respect to the number of glucosamine-galactose units, each group with a constant number of these units. Each group was subdivided by additional sugar residues which were associated with a specific blood group activity. The amino acid composition showed marked similarities and characteristic quantitative relationships. The concept that the isolated glycoproteins have a basic common composition and are built on a similar structural plan was supported by re-chromatography of the glycoproteins on Ecteola-cellulose and Sepharose 4B. The sub-fractions eluted on Ecteola-cellulose showed a similar carbohydrate and amino acid composition and differed only in their sulphate content. Elution on Sepharose 4B provided one retarded peak. Fractions taken from different areas of the peak showed virtually the same carbohydrate and amino acid composition. The IgG, IgM, IgA and α-acid glycoprotein of seven gall bladder bile samples were determined. The results show that the biliary glycoproteins and the immunoglobulins constitute important components of gall bladder bile.