Abstract: A hydraulic brake booster (12) having a housing (100,200) with a first bore (102) separated from a second bore (104). The first bore (102) retains a power piston (50) and the second bore (104) retains a control valve (60). The first bore (102) is connected by a passage (112) to the second bore (104) that is connected to a source of pressurized supply fluid (24). In responsive to a desired braking force being applied to the input member (30,30′), the lever arrangement (80) moves the control valve (60) to allow controlled pressurized supply fluid to be communicated from the second bore (104) by way of passage (12) to the first bore (102).