Paeonia radix is the root of Paeonia aliflora Pallas, which is a perennial plant classified in the family Paeoniaceae. Paeonia radix possesses several pharmacological effects such as analgesic, anti-inflammatory and anti-allergic, anti-oxidative, and anti-coagulant activities. In this study, we investigated the effect of the aqueous extract of Paeonia radix on the lipopolysaccharide-induced inflammation in mouse BV2 microglial cells. The aqueous extract of Paeonia radix at respective concentration was treated one hour before lipopolysaccharide treatment. In the present results, the aqueous extract of Paeonia radix suppressed prostaglandin $E_2$ synthesis and nitric oxide production by inhibiting the lipopolysaccharide-stimulated mRNA expressions of cyclooxygenase-2 and inducible nitric oxide synthase in mouse BV2 microglial cells. These results demonstrate that Paeonia radix exerts anti-inflammatory and analgesic effects probably by suppressing mRNA expressions of cyclooxygenase-2 and inducible nitric oxide synthesis. The present study demonstrates that Paeonia radix may offer a valuable mean of therapy for brain inflammatory diseases.