Abstract: An infusion method and apparatus for infusing liquid into a patient, the infusion apparatus being compatible with a plurality of different types of cassettes which are adapted to be insertable into and removable from the infusion apparatus. The infusion apparatus has a housing adapted to receive a first type of cassette and a second type of cassette, a pump disposed in the housing and adapted to pump liquid through a conduit, and a cassette sensor disposed in the housing, the cassette sensor being capable of determining whether the first type of cassette is inserted into the housing or the second type of cassette is inserted into the housing. The infusion apparatus includes control means for controlling the operation of the pump which causes a first course of control action to be taken when the first type of cassette is inserted into the housing and a second course of control action to be taken when the second type of cassette is inserted into the housing.