The kinetics of photodegradation of the antihistamine fexofenadine hydrochloride using a stability-indicating high performance liquid chromatography (HPLC) method is demonstrated. The degradation was carried out in methanol and in water solutions, prepared from coated tablets, in quartz cells under UV light at 254 nm. The kinetics parameters of order of reaction and the rate constants of the degradation were determined for both solvents. The degradation process of fexofenadine hydrochloride in solutions can be described by second-order kinetics under the experimental conditions used in this study. The obtained results show that the HPLC method is satisfactory in the determination of the kinetics of degradation of fexofenadine hydrochloride in the presence of its photolytic degradation products.