Paeonia radix is the root of Paeonia aliflora Pallas, which is a perennial plant classified in the familyPaeoniaceae. Paeonia radix possesses several pharmacological effects such as analgesic, anti-inflammatory and anti-allergic, anti-oxidative, and anti-coagulant activities. In this study, weinvestigated the effect of the aqueous extract of Paeonia radix on the lipopolysaccharide-inducedinflammation in mouse BV2 microglial cells. The aqueous extract of Paeonia radix at respectiveconcentration was treated one hour before lipopolysaccharide treatment. In the present results,the aqueous extract of Paeonia radix suppressed prostaglandin E2 synthesis and nitric oxideproduction by inhibiting the lipopolysaccharide-stimulated mRNA expressions of cyclooxygenase-2 andinducible nitric oxide synthase in mouse BV2 microglial cells. These results demonstrate thatPaeonia radix exerts anti-inflammatory and analgesic effects probably by suppressing mRNAexpressions of cyclooxygenase-2 and inducible nitric oxide synthesis. The present studydemonstrates that Paeonia radix may offer a valuable mean of therapy for brain inflammatory diseases.