A parking brake system for vehicles, in particular passenger cars, with an extraneous force generating adjusting unit for tightening or loosening at least one actuating pull for a braking arrangement on the vehicle and having an electronic control device whose output variable is used to actuate the adjusting unit. Input variables, in particular from an operating arrangement, sensors and or switches are fed to the control device and the output variable van be varied as a function of the input variable. A force sensor is disposed on or the actuating pull for directly detecting the force exerted thereon. The signals from the force sensor are fed to the control device as an input variable.