Abstract: A non-return valve for medical purposes, in particular for balloon catheters, has a hollow valve housing (3) which at one end has a connecting opening (8) for the insertion of a syringe nozzle and two abutments (16, 17) for a slide member (18). The slide member runs with its peripheral surface over at least one valve opening (15) at the cylindrical inside periphery (14) of the housing (3). The first abutment (16) is of such a slightly raised configuration that the slide member (18) can be inserted through the connecting opening (8), by making use of the elastic deformability of the valve housing (3) and/or the slide member. That makes it possible for the second abutment (17), at the end in opposite relationship to the connecting opening (8), to be already ready moulded in the manufacturing process.