Abstract: A valve having a magnetic armature, which is moved longitudinally in a valve dome; a valve tappet of this armature carries a closing member of a seat valve, which is open when in the rest position. The seat valve is disposed in a valve chamber, from which two pressure fluid conduits lead to face ends of the magnetic armature, which is sealed on its circumference side. When the seat valve is partially open, a pressure is produced in a partial valve chamber by means of a shaping of the valve seat as a hollow cone and of the closing member as a flattened end ball. In the control chamber remote from the closing member, this pressure leads to a movement of the magnetic armature against the tension of a restoring spring, which results in a reduction of the through flow cross section of the seat valve. The valve is particularly useful in slip-controlled hydraulic brake systems of motor vehicles.