Sulfated mucus glycoprotein biosynthesis by human gastric mucosal biopsies was studied. Human gastric healthy specimens and cancer specimens were obtained from antral and corpus normal mucosal areas by biopsy. A comparison was made of the biosynthesized sulfated mucus glycoproteins assessed by the incorporation of 35S-sulfate and 14C-glucosamine into the specimens using an organ culture technique. A significant uptake of 35S-sulfate or 14C-glucosamine into the mucus glycoproteins was demonstrated in all specimens. 14C-glucosamine incorporation into the glycoproteins was almost the same for all biopsies. The synthesis of sulfated glycoprotein in healthy antral mucosa was about four times that in corpus mucosa. Significantly raised levels in sulfated glycoprotein biosynthesis were found in cancer specimens, being about 30 and 13 times higher in antrum and corpus mucosa than that of healthy specimens, respectively.