Objective: Pyungwi-san (PWS) plays a role in a number of physiologic and pharmacologic functions in many organs. Interstitial cells of Cajal (ICCs) are pacemaker cells that generate slow waves in the gastrointestinal (GI) tract. We aimed to investigate the beneficial effects of PWS in mouse small-intestinal ICCs. Methods: Enzymatic digestion was used to dissociate ICCs from the small intestine of a mouse. The whole-cell patch-clamp configuration was used to record membrane potentials from the cultured ICCs. Results: ICCs generated pacemaker potentials in the GI tract. PWS produced membrane depolarization in the current clamp mode. Pretreatment with a $Ca^{2+}$-free solution and a thapsigargin, a $Ca^{2+}$-ATPase, inhibitor in the endoplasmic reticulum, eliminated the generation of pacemaker potentials. However, only when the thapsigargin was applied in a bath solution, the membrane depolarization was not produced by PWS. Furthermore, the membrane depolarizations due to PWS were inhibited not by U-73122, an active phospholipase C inhibitor, but by chelerythrine and calphostin C, protein kinase C inhibitors. Conclusions: These results suggest that PWS might affect GI motility by modulating the pacemaker activity in the ICCs.