The present invention concerns a pump provided with a control module and an attachable fluid reservoir cassette. The control module includes a pumping mechanism for pumping fluid from the fluid reservoir to the patient. The cassette is provided with appropriate indicia to identify differences between a plurality of cassettes. The control module further includes cassette indicia identification structure for identifying indicia on the cassette. One type of cassette identification system includes a projection extending from the cassette and structure associated with the control module which engages the projection. Another type of cassette identification system includes a light reflecting system which utilizes light from the control module and reflected off the cassette. Still other types of cassette identification systems utilize other non-contact switches or sensors to sense indicia on the cassette to identify the cassette from a plurality of cassettes.