Glehnia littoralis (Umbelliferae) is the medicinal plant used traditionally for treatment of immune-related diseases. Prostaglandins and nitric oxide (NO) have been implicated as important mediators in the processes of inflammation and carcinogenesis. For understanding the mechanisms for pharmacological activities of Glehnia littoralis, we evaluated the inhibitory activity of Glehnia littoralis on lipopolysaccharide (LPS)-induced prostaglandin $E_2$ ($PGE_2$) and NO production in mouse macrophage RAW264.7 cells. The results showed that the extract of Glehnia littoralis inhibited LPS- induced $PGE_2$ production effectively, but not NO. Additional study revealed that the extract of Glehnia littoralis suppressed cyclooxygenase-2 (COX-2) expression in a dose-dependent manner. Present study suggests that Glehnia littoralis may have anti-inflammatory and/or cancer chemopreventive activity through the inhibition of $PGE_2$ production by the suppression of COX-2 activity.