The 80 % aqueous acetone extract from the fruit of Piper chaba was found to show protective effects on ethanol- and indomethacin-induced gastric lesions in rats. From the aqueous acetone extract, four new amides named piperchabamides A ( 1), B ( 2), C ( 3), and D ( 4) were isolated, and their structures were determined on the basis of chemical and physicochemical evidence. In addition, the gastroprotective effects of the principal constituents, piperine ( 5), piperanine ( 6), pipernonaline ( 7), dehydropipernonaline ( 8), piperlonguminine ( 9), retrofractamide B ( 10), guineensine ( 11), N-isobutyl-(2 E,4 E)-octadecadienamide ( 12), N-isobutyl-(2 E,4 E,14 Z)-eicosatrienamide ( 13), and methyl piperate ( 14), were examined. As a result, compounds 5 - 10 and 12 - 14 significantly inhibited ethanol-induced gastric lesions at a dose of 25 mg/kg, p. o., while 5, 7, 8, 10, 12, and 13 also significantly inhibited indomethacin-induced gastric lesions at the same dose.