Abstract: An HPLC methodology was developed for determining mequindox residues in the organs of eels.The analysis was conducted under the following conditions: SunFireTM C₁₈ column (4.6 mm×150 mm, 3.5 μm) at 35℃, methanol:deionized water (v/v 40:60) for themobile phase with a flow rate of 0.8 mL·min^-1, and 239 nm wavelength seton PDA detector for optical density measurements. With in the mequindox concentration range of 0.05-2.5 μg·mL^-1, an excellent linear regression between the drug concentration and the peak area under curve was obtained with a correlation coefficient greater than 0.999.LODs of mequindox in the muscle, liver, kidney, and plasma from the eelswere 3 μg·kg^-1, 15μg·kg^-1, 15 μg·kg^-1, and 15 μg·L^-1, respectively. The average mequindox recovery rate of the method ranged from 76% to 90% with RSD (n=6) below 10%. It was, thus, concluded that the newly developed simple, rapidmethodology was highly sensitive and repeatable in detecting mequindox residuein the tissues of the eels.