The oxidation of the insecticide Propoxur by ultraviolet radiation and by the combination of ozone and ultraviolet radiation is studied from experiments carried out in a photochemical reactor. The operating variables considered are temperature, pH, and initial pesticide concentration, plus ozone partial pressure in the combined experiments. In the oxidation by UV radiation, the line source spherical emission model is applied to the experimental data in order to evaluate the radiation flow rate absorbed, and the quantum yields are also determined. In the oxidation by combination of ozone and UV radiation, the kinetic study is performed applying the film theory to the experimental data, and the reaction orders and apparent kinetic constants are deduced.