Abstract: An anti-theft device for a motor vehicle includes an elongate wheel lock bar slidably displaceable within a guide member, the guide member being fixedly securable to the floor board of a vehicle. When so secured and by providing suitable apertures in the floor board and fire wall of the vehicle, the wheel lock bar can be displaced between an inoperative position and an operative position in which the bar will inhibit the normal operation of a front wheel of the vehicle, thereby effectively immobilizing the vehicle. An electric motor is provided for displacing the wheel lock bar via a displacement shaft, operation of the motor being controlled by a control means in a manner that displacement of the wheel lock bar into its operative position will occur automatically upon the vehicle engine being switched off and the vehicle door being opened, whereas displacement into its inoperative position will require transmission of a coded signal to the control means.