The invention relates to a piston pump, in particular for controllable braking systems such as ABS or ESP. The pump is characterized in that a working chamber (40) of said pump is delimited upstream of a piston (3, 52) by a pressure valve. One end of a return spring (4, 51) is supported against a valve seat support (9, 54) of the pressure valve and the other end restores the piston (3, 52) to its lower dead-centre point. Pumps which are to be mass produced should be as inexpensive and easy to assemble as possible. To achieve this, according to the invention, the return spring (4, 51) can also be fixed directly or indirectly to the valve seat support (9, 54).