Abstract: An method for the determination of mifepristone in human plasma by high performance liquid chromatography was developed and validated. The plasma sample was extracted with ether which was removed by evaporation at room temperature under reduced pressure. The residue was taken up with methanol and the solution obtained was submitted to analysis by RP-HPLC. The chromatographic column of spherisorb C18 (250 mm×4.6 mm,i.d. 5 μm) was used in the analysis,and a solution containing methanol,acetonitrile and water mixed in the proportion of 50 to 25 to 25 was used as the mobile phase,passing through the column. Volume of the volumetric loop used was 20 μL. Ultra violet spectrophotometric detection was made at the wavelength of 302 nm with determination by the external standard method. Mifepristone was well separated in the HPLC,thus leading to high selectivity of determination. Linear relationship between the absorbance and concentration of mifepristone was obtained in the range of 0.05 to 10.00 mg·L-1 with a detection limit of 0.01 mg·L-1. Value of average recovery obtained by the recovery test was 98.2%. Precision test was made at 3 different concentration levels,average values of RSD′s (n=5) of within day test and between-day test obtained were 7.0% and 8.3% respectively. Residue of the sample obtained after extraction with ether and removal of ether by evaporation was proved to be stable for at least 7 days when preserved at -20 ℃ in the dry state.