A piston pump as a return pump of a slip-controlled, hydraulic vehicle braking system is disclosed. There is a mushroom-shaped shut-off body as a spring-loaded outlet valve, the shaft thereof extending through a center hole of a tubular damper piston. The shut-off body is movable transversely to the opening and closing direction thereof, so that said shut-off body aligns with a valve seat upon closing. Upon opening, the damper piston forces brake fluid out of a damping chamber in which it is housed so that an opening movement of the outlet valve is dampened.