The aim of this research was to study and to standardize a high-performance liquid chromatography (HPLC) and absorbance ratio method for the determination of hydrochlorothiazide and lisinopril in commercially available pharmaceutical dosage forms. An HPLC method has been developed for the simultaneous determination of hydrochlorothiazide and lisinopril from formulations, using acetonitrile:water (20:80 v/v) (pH 3.8), as a mobile phase at flow rate of 1.0 mlmin−1and LiChrosorb RP -C18column (5 μ, 20cmx4.6 mm), as a stationary phase. Detection was carried out using a UV detector at 213.0 nm. In the second method, an absorbance ratio method, the determination of hydrochlorothiazide and lisinopril was performed by using the absorbances read at 272.0 nm, 258.8 nm and 262.7 nm in the zero-order spectra of their mixture. The absorbance ratio was also developed as a comparison method.