A RP-HPLC method was developed and validated for quantitative determination of Atenolol and Hydrochlorothiazide in pharmaceutical dosage forms. The chromatography was carried out on a 25 cm × 4.6 mm i.d, 5-μm particle, Phenomenex Luna C18 column under reversed-phase partition chromatographic conditions. The mobile phase was a mixture of ammonium acetate (0.02M, pH 4.0 adjusted with glacial acetic acid) and acetonitrile in ratio of 40:60 (v/v) at a flow rate of 1.0ml/min. Clarithromycin was used as an internal standard. The linearity was established in the range of 20 - 400 ng/ml Atenolol and 5-150 ng/ml Hydrochlorothiazide for HPLC. This validated method can be used for estimation of Atenolol and Hydrochlorothiazide in pharmaceutical suspension.