This study focused on the photochemical degradation of two herbicides : isoproturon (IPU) and diuron (DIU), that are two of the most abundant phenylureas found in surface and ground waters in France and classified as prioritary substances by European Directive (DCE). Sunlight irradiation was performed by a solar simulator Atlas Suntest CPS+ (290 nm < λ < 700 nm, 250 W/m2). Pesticide concentrations used in the experiments were approximately 1 µM. Photodegradation efficiencies have been measured for aqueous solutions of IPU and DIU, in the presence of DOM (20 mg/L) isolated from surface waters. LC-MS analysis was performed in order to identify possible photoproducts.