Since gastric mucosal lesions are frequently encountered in patients with liver disease, we measured the levels of gastric mucosal hexosamine. In chronic hepatitis patients, hexosamine levels were reduced in both the antrum and corpus as compared with those in normal controls, while values in the advanced liver cirrhosis group (total bilirubin greater than 5 mg/dl) were lower than in the less advanced group. Although the presence or absence of esophageal varices had no influence on hexosamine, higher concentrations were found in patients with the red color sign (+) in comparison with those with negative red color sign (-). One month after endoscopic injection sclerotherapy of esophageal varices, hexosamine did not change, but decreases were seen in both the antrum and corpus at 3 months. We observed an increase in gastric mucosal blood flow after treatment with teprenone, a new antiulcerative agent, in normal controls. Gastric mucosal hexosamine increased significantly after teprenone treatment in both chronic hepatitis and liver cirrhosis groups. From these results, we conclude that hexosamine has a defensive action against gastric lesions in various liver diseases.