A simple and rapid reversed-phase high performance liquid chromatographic (RP-HPLC) method for the determination of aceclofenac in human plasma has been established. Plasma samples from 18 male volunteers were collected. The samples were extracted with ether, and the extractant was redissolved in the mobile phase after dried by N2 at 37 degrees C. Chromatography was performed on an ODS column with methanol-0.1 mol/L ammonium acetate (pH 6.0) (7:3, v/v) as the mobile phase. The flow rate was 1.0 mL/min. The UV-Vis detector was set at 275 nm. The linear range was from 0.05 mg/L to 40.0 mg/L with a correlation coefficient of 0.9999. The intra-day and inter-day relative standard deviations (RSDs) for assaying the plasma samples containing three levels of aceclofenac were 1.84%-7.13% and 3.40%-9.33% (n = 5), respectively. The mean absolute recovery was 82.5% and the mean relative recovery was 100.3%. This sensitive and selective method can be used for clinical pharmacokinetic study of aceclofenac.