The present study is designed to explore an anti-tumor activity on crude extracts of Oplopanax elatus. Water extractions of Oplopanax elatus were performed at $100^{circ}C$(OeE-100). OeE-100 doses up to $62.5{mu}g/m{ell}$ had no cytotoxicity on the tumor cell lines in vitro. In experimental lung metastasis of colon26-M3.1 carcinoma or B16-BL6 melanoma, the prophylactic intravenous ($4{sim}100{mu}g/mouse$) or oral (2 mg/mouse) administration of OeE-100 significantly inhibited tumor metastasis as compared with tumor controls. Peritoneal macrophages stimulated with OeE-100 produced various cytokines such as TNF-${alpha}$, IL-6 and IL-12. In an analysis of NK-cell activities, i.v. administration of OeE-100 ($10{sim}100{mu}g/mouse$) significantly augmented the cytotoxicity to YAC-1 tumor cells. Vaccination of mice with boiling-treated tumor cells (BT-vaccine) in combination with OeE-100 ($100{mu}g/mouse$) showed higher inhibitions in tumor metastasis when compared with the mice of BT-vaccine treatment. In addition, the splenocytes from OeE-100 admixed BT-vaccine immunized mice secreted a higher concentration of Th1 type cytokine such as IFN-${gamma}$. These results suggested that the OeE-100 stimulated immune system and was a good candidate adjuvant of anti-tumor immune responses.