Two different brands of 500 mg paracetamol tablet: Tylenol and GPO Paracetamol, were evaluated for their relative bioavailability in 16 normal healthy Thai volunteers using a randomized crossover design with 2 weeks washout period. In each treatment, subjects received a single oral 1,000 mg dose of the test product following an overnight fast. Serial twelve venous blood samples of 10 ml were collected before each dose and during 10 hours period after drug administration. Plasma paracetamol concentrations were then analyzed by high performance liquid chromatography (HPLC). Pharmacokinetic parameters including peak plasma concentration (CPmax). time-to- peak (T max) and total area under the plasma concentration-time curve at 10 hours (AUC010) and at infinity (AUG0∞) were calculated. Data analysis by ANOVA and Student's t test revealed that there were no statistically significant differences between Tylenol and GPO Paracetamol in all relevant pharmacokinetic parameters obtained. Therefore, it was concluded that Tylenol and GPO Paracetamol were bioequivalent.