A rheostatic control system for controlling the speed and the direction of rotation of a DC motor which is employed mainly for controlling the speed of an electric vehicle or the like. The system comprises a sliding-contact rheostatic unit which is provided between a DC power supply and a DC motor and which includes stationary contacts and speed controlling resistors, whereby the speed control of the DC motor is accomplished by means of the speed controlling resistors, and the rotation of the DC motor in either direction is controlled by changing the polarity of the voltage applied to the polarity changing terminals of the DC motor.