We investigated whether an aqueous extract of Polygala tenuifolia root (PTAE) inhibits secretion of inflammatory cytokines from primary cultures of mouse astrocytes. PTAE dose-dependently inhibited the Tumor necrosis $factor-{alpha}$ $(TNF-{alpha})$ secretion by astrocytes stimulated with substance P (SP) and lipopolysaccharide (LPS). Interleukin-1 (IL-1) has been shown to elevate $TNF-{alpha}$ secretion from LPS-stimulated astrocytes while having no effect on astrocytes in the absence of LPS. We therefore also investigated whether IL-1 mediated inhibition of $TNF-{alpha}$ secretion from primary astrocytes by PTAE. Treatment of PTAE to astrocytes stimulated with both LPS and SP decreased IL-1 secretion to the level observed with LPS alone. Moreover, incubation of astrocytes with IL-1 antibody abolished the synergistic cooperative effect of LPS and SP. Reverse transcriptase-polymerase chain reaction analysis demonstrated the significantly reduced level of the $TNF-{alpha}$ mRNA was expressed in astrocytes treated with PTAE. These results suggest that PTAE has an antiinflammatory activity on the central nervous system curing some pathological disease states.