The invention concerns a motor vehicle braking system which comprises a controllable pneumatic brake booster (2) whose control valve (19) can be actuated independently of the driver's wishes by an electromagnet (20). A control structure comprising a brake pressure regulator (8) and a control valve position regulator (18) generates signals representing the voltage to be fed to the electromagnet. In order to improve control quality, according to the invention, the brake pressure regulator (8) is formed by a parallel circuit comprising a first regulator (follower regulator (21)), which follows rapid time variations in the signal corresponding to the nominal braking pressure (Pnom), and a second regulator (target value regulator (22)) which follows slow variations or static values of the signal corresponding to the nominal braking pressure (Pnom). The output variables (Snom1, Snom2) of the two regulators (21, 22) are fed to a situation switching logic circuit (55) which switches through the output variables of the first (21) or second regulator (22) to the position regulator (18) depending on the respective selection criterion.