A high-performance liquid chromatography (HPLC) assay has been developed for the determination of glafenine and floctafenine in plasma. Drugs are extracted with ethyl acetate from alkalinized samples using antipyrine as an internal standard. After evaporating the solvent to dryness, the residue is removed and analyzed using a microPorasil 10 micron column with a mobile phase of n-hexane and ethanol (80/20, v/v). The drugs are detected at 240 nm. The lower detection limits are 1.993.10(-2) mumol/l and 3.138.10(-2) mumol/l for glafenine and floctafenine, respectively. The method is simple, rapid and very sensitive. It is the first HPLC method for the determination of floctafenine.