Jeungaektang (JAT) is the herbal formula, has the effect of moistening the dryness by activating lung Qi and by nourishing Yin, has being used for dryness syndromes. Generally the herbal formulae for moistening dryness are used for exogenous or endogenous dryness syndromes. JAT has been clinically used for the treatment of endogenous dryness syndromes. It is composed of Scrophulariae Radix. Rehmanniae Radix and Liriopis Tuber. Recent studies showed that JAT has a protective effect against $CCl_{4}-induced$ hepatotoxicity and anti-inflammatory effects against ear swelling of mouse induced by Crotonis Fructus. However, the effect of JAT on the immunological activity was rarely studied. Therefore, this study evaluated the effects of JAT the regulatory mechanism of nitric oxide (NO) and cytokines in the lipopolysaccharide (LPS)-stimulated RAW 264.7 cells. After the treatment of JAT water extract, cell viability was measured by MTT assay, NO production was monitored by measuring the nitrite content in culture medium. Cyclooxygenase-2 (COX -2) and inducible nitric oxide synthase (iNOS) were determined by immunoblot analysis, and levels of cytokine were analyzed by sandwich immunoassays. Results provided evidence that JAT inhibited the production of nitrite and nitrate ($0.1{sim}1.0$ mg/ml), iNOS ($0.1{sim}1.0$ mg/ml), $interleukin-1{eta}$ ( $0.1{sim}1.0$ mg/ml) and tumor necrosis $factor-{alpha}$ ($0.1{sim}1.0$ mg/ml) in RAW 264.7 cells activated with LPS. Furthermore, JAT inhibited the expression of COX-2 expression and production of prostagladin E2 ($0.1{sim}1.0$ mg/ml). These findings suggest that JAT can produce anti-inflammatory effect, which may play a role in adjunctive therapy in Gram-negative bacterial infections.