Abstract: Electromechanical operating device for a slidingly movable door, which device comprises a motor driving a worm on which is mounted a nut connected to the door which is is to be moved, said nut being secured in respect of rotation by a slide guide having a step at the point corresponding to the end of the stroke of the door. This step allows a certain rotation of the nut and constitutes a stop preventing the rearward displacement of the nut when the latter is acted on by means of the door.The nut is composed of two parts axially fastened to one another and mounted for rotation one about the other, these parts being so shaped as to ensure that they will be fastened together in respect of rotation with considerable angular play.The aim of the device is to prevent untimely unlocking of the closed door through the elastic torsional cocking of the worm.