Prunellae Spica is the spike or whole plant of Prunella vulgaris Linne, which has been used for clearing heat from the liver, brightening the eyes and treating headache in traditional oriental medicines. This study was conducted to evaluate the inhibitory effects of the aqueous extract of Prunellae Spica (PSE; PS extract) on the production of NO and PGE2 in LPS-activated Raw 264.7 cells. Cell viability was determined by MTT assay, and all three doses of PS extract (0.03, 0.1 and 0.3 mg/ml) had no significant cytotoxicity during the entire experimental period. The cells were treated with 1 ${mu}g/ml$ of LPS 1 h before adding PS extract, and increased NO and PGE2 production were detected in LPS-activated cells compared to control. However, these increases were dose-dependently attenuated by treatment with PS extract. The inhibition of NO by PS extract was due to the suppression of iNOS expression via inhibition of $NF{kappa}B$ nuclear translocation and proteolytic degradation of $I{kappa}B{alpha}$. The decreased level of PGE2 was derived from inhibition of COX-2 activity, but expression of COX-2 protein was not affected by PS extract. Moreover, PS extract reduced the elevated production of IL-${eta}$ and IL-6 by LPS. These results demonstrate that PS extract has inhibitory effects on the production of NO and PGE2 as a consequence of the reduction of proinflammatory cytokines, especially IL-${eta}$ and IL-6 in LPS-activated Raw 264.7 cells.