A simple, precise, rapid and accurate RP-HPLC-PDA method has been developed for the simultaneous estimation of Hydrochlorothiazide and Irbesartan in tablet formulations. The chromatographic separation was achieved on Waters Symmetry C18 column (250 mm x 4.6 mm, 5.0 μ particle size) using methanol: THF: acetate buffer (60:10:30v/v) pH adjusted to 5.5 with acetic acid, flow rate was 0.75 ml/min and column was maintained at 500C. Quantification and linearity was achieved at 271 nm over the concentration range of 0.3 – 50 μg /ml for Hydrochlorothiazide and 3.6 - 600 μg/ml for Irbesartan. The method was validated for specificity, linearity, accuracy, precision, LOD, LOQ and robustness. The proposed method was optimized and validated as per the ICH guidelines.