Abstract: An anti-theft system for vehicles pressurizes and locks the hydraulic brakes whenever voltage is removed from a special master brake cylinder. The master brake cylinder has all the conventional parts, but the central rod which carries the hydraulic pistons extends past the usual point and attaches to a permanent magnet at the end of the rod. A coil spring forces the rod in the direction of rod movement needed for brake activation, toward a solenoid. The solenoid is powered by the vehicle battery. The spring is prevented from continuously engaging the brakes by the magnetic repulsion of the permanent magnet by the solenoid. The magnetic force acts to disengage the brakes. When the current is cut off, so is the magnetic repulsion, and the unbalanced force of the spring pushes the rod to engage the brakes. The solenoid current can be switched on or off by a remote switch. The switch may be closed and opened remotely through a radio link.