The role of a hot water extract of black tea (Camellia sinensis (L). O. Kuntze Theaceae) in the gastric cytoprotective mechanisms was studied using gastric mucosal lesions produced by various ulcerogens in rats as an experimental model. Prior oral administration of black tea extract (BTE) at 20 ml/kg, i.g. once a day for 7 days significantly reduced the incidence of gastric erosions and severity induced by ethanol, diethyldithiocarbamate (DDC) and diethylmaleate (DEM). This treatment also favorably altered the changes in acid and peptic activity of gastric juice in these ulcerogen-treated animals. Singular administration of succimer (60 mg/kg, i.g.), the standard sulfhydryl containing antiulcer drug used as a reference drug, was also effective. The levels of glutathione and glutathione peroxidase were significantly decreased after treatment with ethanol, DDC and DEM, and this decrease was prevented by BTE pretreatment in the aforesaid manner. Other major features of BTE-induced reversal of ulcerogenic agents include a significant decrease in the protein content and a marked increase in hexosamine and sialic acid content. These results suggest a major role for glutathione, an endogenous antioxidant, in the cytoprotection against ulceration afforded by BTE.