A simple, sensitive, reproducible, accurate and precise RP-HPLC method was developed for simultaneous estimation of Irbesartan and Hydrochlorothiazide in tablet dosage form. The chromatographic separation was achieved on Quails 5 BDS C18 column (250 x 4.6mm, particle size 5µ) in low pressure gradient mode with mobile phase Acetonitrile: water (pH adjusted to 3.3 with orthophosphoric acid)in the ratio (42:58 v/v). The flow rate and injection volume were 1.1ml/min and 10 µL respectively and monitored on a PDA detector at 254nm. The developed method was found to be linear for Irbesartan and hydrochlorothiazide in the range of 12-84µg/ml and 1-7µg/ml with correlation coefficient (r2 ) 0.9997 and 0.9992 respectively. The proposed method was validated as per ICH Q2B guidelines. Assay of the marketed formulation was found to be 98.26% and 98.47% for Irbesartan and hydrochlorothiazide respectively. In accuracy study the percentage recovery at three different levels was found to be in the range of 98.80% to 101.78%.