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℃(OeE-100). OeE-100 doses up to 62.5 ㎍/㎖ 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 (4~100 ㎍/mouse) or oral (2 ㎎/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-α, IL-6 and IL-12. In an analysis of NK-cell activities, i.v. administration of OeE-100 (10~100 ㎍/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 ㎍/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-γ. These results suggested that the OeE-100 stimulated immune system and was a good candidate adjuvant of anti-tumor immune responses.