An appliance for water-jet surgery is provided that includes a plurality of supply cylinder and piston arrangements in each of which is stored a working fluid that can be expelled, by means of the piston, through an outlet into a pressure conduit. At least one actuation device is provided to actuate the piston of each supply cylinder. By means of a change-over device to change the actuation from the piston of one supply cylinder to the piston of another supply cylinder, it is ensured that the working fluid can be expelled into the pressure conduit from consecutively emptying supply cylinders. As a result, an apparatus with a small structure that is achieved by simple means is disclosed.
