In this study we investigated the effects of constituents of Amomum xanthioides (AX) on gastritis in rats and on the growth of human gastric cancer cells. The ethanol extract of Amomum xanthioides significantly inhibited HCI ${cdot}$ ethanol-induced gastric lesions and the growth of Heli-cobacter pylori (H. pylori). The ethanol extract of AX was further fractionated with hexane, chloroform, butanol and H$_2$O. Among these fractions, oral treatment with the butanol fraction at a dose of 350 mg/kg was the most effective at preventing HCI ${cdot}$ ethanol-induced gastric lesions. In pylorus ligated rats, the butanol fraction also decreased the volume of gastric secretion and gastric acid output. We isolated six subfractions of the butanol fraction using open column chromatography. Subfraction 4 (150 mg/kg) significantly inhibited HCI ${cdot}$ ethanol-induced gastric lesions and gastric secretion in pylorus ligated rats. Using GC-MS we identified the constituents of subfraction 4 to be five aliphatic compounds, 1-hexadecene, 1-nonadecene, cycloeicosane, 1 -octadecene and cyclotetracosahe. In addition, subfraction 4 reduced cell viability in a dose-dependent manner in human gastric cancel cells (AGS, KATOlll and SNU638). It also increased intracellular Ca$^{2+}$ concentration in SNU638 cells, an effect that was significantly inhibited by dantrolene, a Ca$^{2+}$ release blocker. Moreover, dantrolene significantly inhibited subfraction 4-induced cytotoxicity. Taken together, these results suggest that subfraction 4 of the butanol extract of AX has an anti-gastritic effect in rats and is cytotoxic to human gastric cancel cells. The mechanism of its anti-gastritic action may be associated with the inhibition of secretion of gastric acid and anti-H. pylori action. Its cytotoxicity against human gastric cancer cells may be, at least in part, mediated by intracellular Ca$^{2+}$ dyshomeostasis. From these results, we suggest that AX may be useful for the treatment of gastritis and gastric cancer.