The purpose of this study was to determine the pharmacokinetics and comparative bioavailability of atenolol tablets manufactured by two different drug companies. Pharmacokinetics (PK) and comparative bioavailability of atenolol tablets manufactured by two different drug companies were investigated in 12 healthy volunteers in an open, randomized cross-over trial. After a single oral dose of 100 mg atenolol tablets, the concentration of atenolol in plasma was determined by a modified high performance liquid chromatographic (HPLC) method with fluorimetric detection. Intra-day and inter-day coefficients of variation (CV) were within 12%. The detection limit was 0.02mg/L for plasma samples. The average bioavailability and pharmacokinetic parameters of the two atenolol tablets were as follows: peak plasma concentration (Cmax): 0.98 ± 0.39 mg/L, 0.85 ± 0.32 mg/L; time to peak plasma concentration (Tmax): 2.88 ± 1.03 hours, 2.96 ± 1.16 hours; plasma half-life (T1/2): 6.19 ± 1.01 hours, 6.19 ± 1.38 hours; area under the plasma concentration-time curve (AUC0→∞): 8.74 ± 3.85 mg-hr/L, 7.88 ± 2.69 mg-hr/L; AUC0→28: 8.34 ± 3.66 mg-hr/L, 7.50 ± 2.61 mg-hr/L; area under the first moment-time curve (AUMC): 81.03 ± 37.62 mg-hr2/L, 74.86 ± 26.67 mg-hr2/L; mean residence time (MRT): 9.27 ± 0.75 hours, 9.50 ± 1.35 hours for Ateol® tablets (Standard) and Tenormin® tablets (ICI), respectively. No statistically significant differences were observed for the PK parameters between the two products (p > 0.05). The narrow CI90% values, high power values and the results of two one-sided t-tests also showed that the two products are very similar. The PK parameters obtained in this study are similar to those reported previously.