The invention relates to a piston pump for a slip-controlled hydraulic vehicle brake system. To make a piston of the piston pump easy and inexpensive to manufacture, the invention proposes that the piston be comprised of a sleeve-like shaped part and a valve seat part that is made of plastic and is press-fitted into the shaped part. A high-pressure-side sealing lip is formed onto the valve seat part and is of one piece with it. By means of a tubular support body, a restoring spring is supported on the valve seat part spaced apart from a valve seat of the valve seat part and spaced apart from the sealing lip, which prevents the valve seat and the sealing lip from being impaired by the force of the restoring spring.