A process is described for the production of an oriented, heat-set polyester film including an admixture of polydiorganosiloxane in the amount of 0.001 to 2% by weight, as well as further additives, such as inert inorganic and/or organic particles. The thermoplastic material is melted in an extruder and extruded through an appropriate die to give a cast film, is then quenched, reheated, stretch oriented, and heat set. The characteristic criteria is the addition of the polydiorganosiloxane to the polydiorganosiloxane-free polyester in the form of a masterbatch.