Abstract: A disposable cassette containing a fluid pump for use with a main unit including apparatus for driving the pump is disclosed which cassette utilized a piston-type pump in conjunction with active valves to pump fluid. The inlet and outlet channels in the cassette are formed by a diaphragm covering open channels in the cassette body, and the same diaphragm is used to form the active valves, which are actuated by valve actuators in the main pump unit. Additional features of the cassette include an air trap upstream from the pump, and an integral clamp which allows priming of the cassette.