Many traditional herbal remedies exhibit several beneficial effects including anti-inflammation. The exact mechanism of the a-inflammato action of Panax notoginseng Buck F.H. Chen. however, has not been determined. In the present study, we have isolted the acting compound, emodin, from P. notoginseng and examined the effects of p. notoginseng and emodin on lipopolysaccharide (LPS)-induced nitric oxide (NO) production, and inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) gene expression in RAW264.7 macrophages. The results indicated that p. notoginseng concentration-dependently inhibited LPS-induced NO production. Furthermore, P. notoginseng inhibited the expression of LPS-induced iNOS and COX-2 proteins without an appreciable cytotoxic effect on RAW264.7 cells. Emodin also inhibited LPS-induced iNOS protein as potently as P. notoginseng. This was consistent with the findings that P. notoginseng but not emodin inhibited prostaglandin E2 synthesis induced Dy LPS.