Abstract: Following detailed study,a rapid and sensitive assay for ethmozine in humanplasma has been developed using reversed phase high performance liquid chromatography(HPLC).Plasma samples were prepared for analysis by addition of internal standard(5-chloro-2-amino-benzophenone )followed by protein preci pitation using acetonitrile.A nalytical column was a C 18 spherisorb.The mobile phase consisted of mathanol—water—triethylamine(70 :30:0.4,v/v/v,pH6.5).The column effluent was monitored at 268 nm. The calibration curve was linear in the rangefrom 20 ng/ml to 4000 ng/ml with r=0. 9994.The detection limit of this method was 3 ng/ml.Themethed showed good precision and the analytical recovery of ethmozine from plasma was 90～105%;The relative standard deviations for within- day and between- day were 2.4～6;3%and 4.5～10.2%respectively.The plasma drug concentration- time course in man after oral administration of 400 mgafter conformed to a 1-compartment open model with a first order absorption phase.Mean T1/2valuewas 1.75+0.45h.