an actuating unit for a hydraulic brake system for automotive vehicles includes a vacuum brake power booster and a master brake cylinder . to transmit the reaction forces , developing during actuation in the master brake cylinder , to a vehicle body wall which carries the actuating unit , a centrally positioned force - transmitting element is provided , which is arranged between the master brake cylinder and the vehicle body wall in terms of effect . the force - transmitting element is formed of a continuous bolt which extends in an axial direction through the control housing of the vacuum brake power booster .