Abstract: A brake system including an apparatus for limiting drive slip at drivable vehicle wheels by feeding brake pressure into wheel brakes associated with these vehicle wheels. The brake pressure is generated in a pressure modulator having a spring-loaded stepped piston including a primary piston. The primary piston can be acted upon by pressure fuid from a supply container by a motor which drives a pump. A secondary piston of the stepped piston effects the brake pressure and feeds it via a valve assembly into a brake line extending between the master brake cylinder of the brake system and a wheel brake. The brake pressure can be diminished by controlling the drive motor of the pump. The pump is embodied with reversible pumping directions, and the pressure fluid flows through it both during a working stroke and a return stroke of the stepped piston. The valve assembly is actuatable by the stepped piston as a function of the position thereof.