Abstract: A brake pressure regulator for an hydraulic vehicle braking system. A first inlet chamber (14) and an outlet chamber (20) for a first brake circuit (HzI-RzI) are defined by piston surfaces of different sizes of a stepped piston (30) which controls a valve (40) disposed in a connection between these two chambers (14, 20). The pressure in a second inlet chamber (24) adapted to be connected to a second brake circuit (HzII-RzII) acts on an annular control piston (50) which is acted upon in opposite direction by a spring (60). The control piston (50) surrounds the stepped piston (30) without contacting the same and is sealed radially inwardly against a plug (16) which is inserted in the housing (10) and which in turn surrounds the stepped piston (30) in sealing fashion. When as switching pressure in both brake circuits (HzI-RzI, HzII-RzII) is surpassed, the stepped piston (30), aided by the control piston (50), adopts a position at which the valve (40) closes.