A cruise control system for an automotive vehicle with a manual or automatic transmission, includes an inhibition circuit. The inhibiting circuit blocks communication between a power supply and an actuator and/or a controller when the manual transmission is set in a predetermined gear or when the automatic transmission is set in a driving range other than the drive range, so as to inhibit the controller from operating in the cruise control mode. When the vehicle is provided with an automatic transmission which is selectively set in first, second, third or fourth gear while the shift lever is set in the drive range position, the cruise control system includes a first inhibiting circuit which blocks the communication when the shift lever is set in a position other than the drive range position, and a second inhibiting circuit which blocks the communication when the automatic transmission is set in either the first or second range while the shift lever is set in the drive range position.