HPLC is a magic tool for drug analysis. This book contains development of new analytical methods of angiotensin receptors antagonists (ARA-II)in their dosage forms and in combination with the main diuretic drug (Hydrochlorothiazide). New methods depends on some chromatographic theories and rules to separate analyzed drugs. All developed method were validated according to ICH guideline (Q2R1). ARA-II were subjected to stress studies according to ICH guidelines to elucidate stability of the drugs and separate the main degradation products.