Pure sulphated glycoproteins may be isolated from human gastric and salivary secretions following proteolysis with pepsin and precipitation with cetylpyridinium chloride. The sulphated glycoproteins are present only in low concentration in parotid saliva and in much higher concentration in saliva from the submaxillary glands. In the same patient, the chemical composition of the salivary and gastric sulphated glycoproteins is very similar. Quantitative analysis by gas liquid chromatography of the four chief sugar components (galactose, fucose, glucosamine, galactosamine) give very close figures for sulfated glycoproteins isolated from the saliva or gastric juice. The sulphate content was the same, as was the electrophoretic mobility. The similarity between salivary and gastric sulphated glycoproteins might suggest contamination of the gastric juice with saliva but comparison of their concentration in saliva and in gastric juice excludes this possibility. There exist important differences in the output and composition of the salivary and gastric glycoproteins secreted by different subjects. These differences may be related to the ABO blood group and secretor systems or to some pathological condition.