The mechanism of phagocytic activity of the ethyl alcohol fraction of Cervus nippon (CN-E) was investigated in vivo. The administration of CN-E (100 mg/kg, p.o.) enhanced lucigenin chemiluminescence and the engulfment of fluorescein-conjugated E. coli particles in murine peritoneal macrophages. Phagocytic activity was suppressed by the treatment of S-nitrosoglutathione (GSNO) which is an exogenous nitric oxide donor depending on the concentration of dose. CN-E suppressed the production of nitric oxide and enhanced the concentration in [Ca2+](i). The enhancement in [Ca2+](i) was diminished by the treatment of EGTA. These results indicate that CN-E enhances the phagocytic activity of murine peritoneal macrophage via a suppression of nitric oxide production and an increase in [Ca2+](i).