The simultaneous liquid chromatographic determination of the enantiomers of both fluoxetine and its metabolite norfluoxetine in plasma samples of treated patients is described. The compounds are subjected to solid phase extraction before chromatography. The separation of the analytes is achieved using two chiralcel ODR columns on-line coupled and a mobile phase consisting of acetonitrile-NaClO40.3M (66/34 v/v, pH 2.5) at a flow rate of 0.6 mL/min. The compounds were detected by ultraviolet absorbance at 220 nm. The limit of quantification for each compound was 10ng/mL.