1. Objectives The purpose of this study was to investigate the effects of the enzyme activity of Palmulgunja-tang with administered orally solution on cytochrome P450 isozyme 2. Methods This study was carried on through following methods. We treated the rat with the {3-naphthoflavone (${eta}NF$) of 80mg/kg for 3 days i.p injection. Firstable, microsomal protein was separated and total intracellular protein test was done. Then GOT and GPT were measured and assay of cytochrome P450 IAI/2 enzyme activity was performed according to the method of EROD and MROD. (Ethoxyresorufin-O-deethylase(EROD) activity was used to measure cytochrome P450 lAI activity and methoxyresorufin O-demethylase(MROD) activity was used to measure cytochrome P450 lA2 activity. ) 3. Results and Conclusions 1) PGT recovered the liver damage on ${eta}NF$ inducible CYP IAI/2 by pre-post and high-low condition. 2) At concentration of post-treated 50mg!kg of PGT, the inhibiting of $etaNF$ metabolites to liver of rat cytochrome P450 lAl was inhibited by 53.0% respectively. 3) PGT showed 36.0% inhibition of ${eta}NF$-induced lA2 activity at the concentration post-treated 50mg/kg.