Abstract: A hydraulic lock-up anti-theft system which energizes and holds the braking system in the active mode for vehicles in the park position and which includes provisions for ignition interlock to prevent vehicle start-up and provides an alert signal, if mechanical tampering with the systems occurs, is presented. Improvement over the prior art include ability to operate under any environmental temperature variations, elimination of any potential valve seating vibration induced degradation, elimination of necessity for cam position braking mechanisms, minimization of activation loads in manual arming and positioning and the ability to add parallel and independent activation circuits to the design.