Chromatographic separation of naproxen has been studied using hydroxypropyl-beta-cyclodextrin as chiral mobile phase additive. The effects of mobile-phase composition were researched in detail. The appropriate composition of mobile phase was 85:15 (v/v) aqueous with 0.5% TEA at pH 3.5/ ethanol containing 25 mM HP-beta-CD, and the column temperature was set of 25 degrees C. Graphs of 1/ k versus [HP-beta-CD] gave good linear relationships, indicating the stoichiometry ratio of naproxen with HP-beta-CD of 1:1. Apparent thermodynamic parameters were also calculated from the plots of ln alpha versus 1/T, it was found that the enantioseparation was enthalpy driven and the inclusion process was exothermic.