Abstract: A piston pump, in accordance with several embodiments, comprises a suction chamber into which fluid medium enters from an inlet line via a suction valve, beginning at the outset of a delivery stroke of the piston pump, without a build-up of intake negative pressure during the delivery stroke of the piston, and is particularly adapted to prevent vapor bubble formation. A reliable pump closure is ensured in the vicinity of the pump outlet, independent of the spring action of a return spring, which bears against the piston, in that any fluid medium entering the suction chamber of the pump contacts the piston in a direction producing reinforcement of the outlet closure pressure. In accordance with preferred embodiments, the piston may be a partially hollow or entirely hollow piston instead of a solid one.