To search for immunoactive natural products exerting anti-inflammatory activity, we have evaluated the effects on the water extracts of Artemisia princeps Pampanini (APP) on lipopolysaccharide-induced nitric oxide (NO), tumor necrosis factor-α (TNF-α), and prostaglandin E2 (PGE2) production by RAW 264.7 macrophage cell line. Our data indicate that this extract is a potent inhibitor of NO production and it also significantly decreased PGE2 and TNF-α production. Consistent with these results, the protein and mRNA expression level of inducible NO synthase (iNOS) and cyclooxygenase-2 (COX-2) was inhibited by water extracts of APP in a dose-dependent manner. These results suggest that APP may exert anti-inflammatory and analgesic effects possibly by suppressing the inducible NO synthase and COX-2 expressions.