Abstract: A tandem master cylinder for hydraulic brake systems of automotive vehicles comprising a housing in whose bore a first and a second piston are sealingly and slidably disposed. The piston in the inactive position abut on stops in the housing under the action of a first and a second resetting spring and which, within the bore, confine a first and a second pressure chamber which are in communication with a first and a second unpressurized supply chamber via central valves that are open when in the inactive position. The first piston-resetting spring is anchored on the second piston, and its spring rate is greater than the spring rate of the second piston-resetting spring.