A simple, selective and precise stability-indicating liquid chromatographic method is developed and validated for determination of two antihyperlipidemics; rosuvastatin calcium (RSV) and ezetimibe (EZE) in presence of their acid degradation products. Multiple peaks of degradation products of each drug were well separated from peak of the intact. Besides, when RSV and EZE are in mixture, their peaks are well separated from peaks of degradation products. The method is based on isocratic elution of RSV, EZE and their degradants on a reversed phase C18 column (250mm ⇥ 4mm, 3/mum) – YMC using a mobile phase consisting of methanol–acetonitrile– sodium dihydrogen phosphate (pH=3.2;0.02 M) (10:38:52,v/v/v). Quantitation was achieved with UV detection at 242 nm. Linearity, accuracy and precision were found to be acceptable over concentration range of 0.1–200 /mug mL 1 for both drugs. The proposed method was successfully applied to the determination of cited drugs in bulk and pharmaceutical preparations, and then used to study the kinetics of RSV and EZE acid degradation that was found to follow a first order reaction. The activation energy was estimated from Arrhenius plot and integrated equation, was found to be 8.727 kcal mol 1 and 9.110 kcal mol 1 for RSV and EZE, respectively.