In this report, the inhibitory action of eupatilin was investgated by using leukotriene D4 in the human neutrophils and Kato III cells (Gastric adenoma cells as a substitute for gastric mucosal cells) stimulated by Helicobacter pylori. Leukotriene D4 (LTD4) was released from both neutrophils and Kato III cells when these cells were incubated with H. pylori. The release of LTD4 increased time-dependently and the maximum release of LTD4 was 2.3∼2.5 pmol. But in the presence of eupatilin, the release of LTD4 from these cells was inhibited in a dose-dependent manner. In the neutrophils, the release of LTD4 was suppressed to 70% and 50% of the control levels when neutrophils was incubated with 0.01 and 0.1 mM of eupatilin. In the Kato III cells, the release of LTD4 was suppressed to 59% and 27% of the control levels by adding 0.01 and 0.1 mM of eupatilin. We estimated the intracellular Ca2⁢ levels when Kato III cells and neutrophils were stimulated by H. pylori using 45Ca. But the suppressive effect of eupatilin on Ca2⁢ influx into these cells was not significant. We also obtained the results that H. pylori induced Ca2⁢ influx into these cells by confocal microscopy, however there was no differences in the dose level of eupatilin. These results were confirmed by 1H Nuclear Magnetic Resonance(NMR) spectroscopy. The NMR patterns of eupatilin in the absence of Ca2⁢ was changed compare with when Ca2⁢ was present, but its effect was not strong.