A simple RP-HPLC method was developed for the determination of hydrochlorothiazide and bisoprolol fumarate in their combined pharmaceutical formulations. The separation was achieved using Cyanide column (250 × 4.6mm, 5μm particle size), both components were determined by UV detector at fixed wavelength at 228nm, for simplicity of the method an isocratic elution was selected, the optimized mobile phase was composed of methanol and buffer solution (pH=5.0) at 82:18 ratio, with flow rate of 0.9ml/min, injection volume was 10μl, and the separation was performed at 30 ^ͦ C. The RSD values was found to be not more than 2.0% so it is acceptable according to USP and ICH. The proposed method was found to be precise and robustness of the method was assessed by assaying test solutions under different analytical conditions deliberately changed from the original conditions such as column temperature, flow rate and detection wavelength. RSD for the area at all different conditions for target.