The purpose of this study was to find out whether the bioavailability of a 550 mg naproxen sodium (CAS 22204-53- 1 ) tablet (Sunprox, test) produced by Sunward Pharmaceutical Sdn Bhd was equivalent to that produced by the innovator. The pharmacokinetic parameters assessed in this study were area under the plasma concentration-time curve from time zero to 72 hours (AUC t ), area under the plasma concentration-time curve from time zero to infinity (AUC inf ), the peak plasma concentration of the drug (C max ), time needed to achieve the peak plasma concentration (t max ), and the elimination half life (t 1/2 ). This was a randomized, single blind, two-period, cross-over study which included 26 healthy adult male and female subjects under fasting conditions. In each of the two study periods (separated by a washout of one week) single dose of test or reference drug was administered. Blood samples were taken up to 72 h post dose, the plasma was separated and the concentration of naproxen were determined by HPLC-UV method. In this study, the mean AUC t , AUC inf , C max , and t ½ of naproxen from the test drug were 936.11 μg.h.mL -1 , 977.03 μg.h.mL -1 , 76.55 μg/mL, and 15.11 h, respectively. The mean AUC t , AUC inf , C max , and t ½ of naproxen from the reference drug were 969.77 μg.h.mL -1 , 1013.72 μg.h.mL -1 , 75.92 μg/mL, and 15.11 h, respectively. The median t max of he test drug and reference drug were 3.0 h and 2.0 h, respectively. The geometric mean ratios (90% CI) of the test drug/ reference drug for naproxen were 96.46% (94.30 – 98.66%) for AUC t , 96.33% (94.03 – 98.69%) for AUC inf , and 100.37% (95.90 – 105.05%) for C max . Based on this study, it can be concluded that the two naproxen sodium tablets (test and drug reference drug) were bioequivalent in term of the rate and extent of absorption.