The present study was designed to explore an immunostimulating activity of crude extracts of Macrolepiota procera, and a combination therapy of cisplatin and Macrolepiota procera extracts which can potentiate the anti-cancer activity of cisplatin. For these, water extraction of Macrolepiota procera were performed at $4^{circ}C$(MPE-4) and $100^{circ}C$(MPE-100). In experimental metastasis of colon26-M3.1 cells, prophylactic intravenous administration of MPE ($80-2,000{mu}g$/mouse) inhibited tumor metastasis compared with tumor control. Peritoneal macrophages stimulated with MPE produced IL-12 as well as induced tumoricidal activity. In an analysis of NK-cell activity, i.v. administration of MPE ($200{mu}g$/mouse) significantly augmented NK cytotoxicity to YAC-1 tumor cells. The combination treatments of cisplatin ($20{mu}g$) and MPE ($100{mu}g$) exhibited prolongation of lifespan in colon26-M3.1 tumor bearing mouse. These results suggested that MPE stimulate immune system non-specifically and application as adjuvant in cancer treatment.