Bioavailability and bioequivalence studies play a major role worldwide and thus attract considerable attention globally in the development phase for both their new drug products and generic equivalents. Bioequivalence is a revolutionary strategy to introduce generic equivalents of branded drugs to lower the cost of medication through proper assessment as directed by the international regulatory authorities. The present study had been performed to explore interchangeability of branded generic drug products by comparing their bioavailability via in vivo study of four different brands. For each study period a set of 12 subjects completed both period with a 1O-day washout period. In both studies, the study formulations were administered after a 1O-12 hour overnight fast. For pharmacokinetic analysis, blood samples were drawn at baseline, O.25, O.5, O.75, 1, 1.5, 2, 2.5, 3, 4, 6, 8, 12 and 24 hours after administration. Plasma concentrations of telmisartan were determined using HPLC coupled with a UV detector. All formulations were considered bioequivalent when evaluated against 9O% CI for the mean ratios were within the predetermined ranges of 8O% to 125%.in study the ratio analysis of AUCO-t for T1, T2 and T3 were 96%, 99% and 91%; Cmax was 98%, 99% and 95%; AUCO-T was 98%, 1O1% and 92%; AUCO-∞ was 1O8%, 112% and 87%; and Kel were found 1O2%, 1O6% and 1O5% respectively. In both studies periods, All Test formulations met the regulatory requirements to assume bioequivalence, based on the rate and extent of absorption.