Two new, rapid, precise, accurate and specific chromatographic methods for the simultaneous determination of Olmesartan medoxomil and Hydrochlorothiazide in combined pharmaceutical dosage forms. The first method based on reverse phase liquid chromatography by using INERTSIL ODS C18 3V (150 x 4.6, 5μ) using mobile phase 1ml triethanolamine in one litre water and the pH was adjusted to 2.5 with orthophosphoric acid and acetonitrile using a gradient program with a flow rate of 1ml/min, throughout the gradient program with a detection wavelength of 225nm.The second method involved silica gel 60F254 high performance thin layer chromatography and densitometric detection at 270nm using chloroform : methanol(85:15) as the mobile phase