The potential of phenanthrene to induce xenobiotic responses was investigated. Olive flounder (Paralichthys olivaceus) was exposed to different levels of phenanthrene $(0.5,;1;and;{mu}M)$ for 4 weeks, Gill CYP450 content and EROD (ethoxyresorufin O-deethylation) activity were found to be significant in the flounders treated with the higher concentration of phenanthrene $(>1.0;{mu}M)$, however, there were no significant changes in gill PROD (penthoxyresorufin O-deethylation) activity in all treated group compared to the controls. This study demonstrated that phenanthrene has potential to induce gill cytochrome P450 and EROD enzyme in olive flounder.