Using cuprolinic blue as a stain along with enzymic digestion, heparan sulphate has been identified as the main glycosaminoglycan in the basement membrane of human gallbladder epithelium. The amount of glycosaminoglycans was quantified by counting the number of molecular profiles cm-2 in electron micrographs of mildly, moderately and severely inflamed gallbladders. There is a significant increase (P = 0.009) in the amount of glycosaminoglycans in the basement membranes of severely inflamed gallbladders compared with cases of mild chronic cholecystitis. Differences, although present, are less significant when mild and moderate or moderate and severe cholecystitis are compared. The findings suggest that there is a continuous accumulation of heparan sulphate in the basement membrane in chronic cholecystitis which increases in amount with the severity of inflammation.