The effects of bitter cardamon (the fruit of Alpinia oxphylla), used as a medicine and a condiment, on HCl/ethanol-induced gastric lesions in rats were examined. The acetone extract at 50 mg/kg, p.o. significantly inhibited gastric lesions by 57.0%. An analysis of the active constituents in the acetone extract was performed using column chromatography. Nootkatone at 20 mg/kg, p.o. significantly inhibited gastric lesion. These results suggest that nootkatone, the sesquiterpenoid is an important constituent in stomach medications containing bitter cardamon.