Objective : This experiment was performed in order to study the effect of an aqueous extract of Salviae radix root(SRRAE) on NO production and NOS gene induction from macrophages Methods : To investigate dose-dependent effects of SRRAE for NO release on the $rIFN-{gamma}-treated$ macrophages, the cells were incubated for 6 hrs in a medium containing $rIFN-{gamma}$ (5 U/ml), stimulated with SRRAE and incubated in a CO2 incubator. The cells were treated with 5 U/ml $rIFN-{gamma}$ plus 100 g/ml of SRRAE, Then, the cells were incubated with various concentrations of NGMMA at $37^{circ}C$ for 48 hrs, Results : SRRAE had no effect on NO production by itself, whereas recombinant $interferon-{gamma}(rIFN-{gamma})$ alone showed modest activity, When SRRAE was used in combination with $rIFN-{gamma}$, there was a marked cooperative induction of NO production in a dose-dependent manner. The optimal effect of SRRAE on NO production was shown at 6hrs after treatment with $rIFN-{gamma}$. The SRRAE-induced production of NO was inhibited by NG-monomethyl- L-arginine(NGMMA) and arginase. $rIFN-{gamma}$ in combination with SRRAE showed a marked increase of the expression of the inducible NOS(iNOS) gene. In addition, the effect of SRRAE was mainly dependent on the SRRAE-induced tumor necrosis $factor-{alpha}(TNF-{alpha})$ secretion. Conclusions : SRRAE induces NO production from macrophages as a result of SRRAE-induced $TNF-{alpha}$ secretion. SRRAE may provide a second signal for synergistic induction of NO production in macrophages already induced to express iNOS gene by $rIFN-{gamma}$.