The invention relates to a method for obtaining a criterion for detecting obstacles in a closure movement of a motor-driven opening. The obtaining method includes the step of determining a speed of rotation of a motor shaft and the step of determining a quantity representative of a motor voltage. The detection criterion is then obtained by a step for calculating the criterion according to the speed of rotation of the motor shaft and the quantity representative of the motor voltage. This makes it possible to obtain a criterion, which is both robust and inexpensive, for detecting obstacles in a closure movement of a motor-driven opening.