Eleutherococcus senticosus is a typical oriental folk medicinal herb. It has been used clinically as a anti-rheumatic disease, anti-stress, ischemic heart disease and gastric ulcer. In the present study, we examined the adjuvant activity of the crude polysaccharides fraction from Eleutherococcus senticosus, EN-3, on the induction of humoral and cellular immune responses against bovine serum albumin (BSA) or ovalbumin (OVA). The thioglycollate-induced macrophages and silica-induced dendritic-like cells cultured with BSA and EN-3 synergistically increased the production of TNF-$alpha$ and IL-12. When mice were subcutaneously immunized with BSA + EN-3, the antibody titer against BSA was showed significantly higher than those immunized with BSA alone. In addition, when mice were immunized with OVA + FIA + EN-3, the antibody titer was showed similar patterns with the FCA. The assay for determining subisotype of antibody revealed that EN-3 augmented OVA-specific antibody titer of IgG1 and IgG2b. The culture supernatant obtained from splenocytes of mice treated with OVA + FIA + EN-3 also showed a higher level of both OVA-specific Th1-type (IL-2, IFN-${gamma}$ and GM-CSF) and Th2-type cytokine (IL-4, IL-6 and IL-10). In vitro analysis of T cell proliferation to OVA on 8 weeks, the splenocytes of mice treated with OVA + EN-3 showed a significantly higher proliferating activity than those treated with OVA alone. These results suggest that EN-3 may possess adjuvant activities to potentially to enhance humoral as well as cellular immune response.