A peristaltic pump device comprising: a platen having a platen surface; a tube positioned adjacent to the platen surface; a cam (30, 30a) that rotates about a rotational axis, said cam having a cam surface that is spaced apart from the platen surface; and a plurality of fingers, each finger having a first portion in cooperative engagement with the cam surface, a second portion adjacent the platen surface, a spring for urging the finger in a direction away from the platen surface and a longitudinal axis that is substantially parallel to the rotational axis of the cam, said fingers being in engagement with the cam surface such that, as the cam rotates about the rotational axis, the fingers will move axially back and forth, sequentially compressing the tube against the platen surface and thereby causing peristaltic movement of fluid through the tube; characterised by a door that may be opened and closed to allow access to the tube; wherein: the tube is mounted on or in a cassette and the door may be opened to gain access to allow removal of the cassette having the tube thereon or therein and replacement thereof with another cassette having another tube thereon or therein, at least one alignment surface is formed in the door, said alignment surface being configured to register with the cassette when the door is closed, thereby holding the cassette in a desired alignment, and the platen surface is provided on an inner surface of the door and at least one indentation is formed in said platen surface such that the tube will be substantially juxtaposed to the platen surface when the door is closed. a platen having a platen surface; a tube positioned adjacent to the platen surface; a cam (30, 30a) that rotates about a rotational axis, said cam having a cam surface that is spaced apart from the platen surface; and a plurality of fingers, each finger having a first portion in cooperative engagement with the cam surface, a second portion adjacent the platen surface, a spring for urging the finger in a direction away from the platen surface and a longitudinal axis that is substantially parallel to the rotational axis of the cam, said fingers being in engagement with the cam surface such that, as the cam rotates about the rotational axis, the fingers will move axially back and forth, sequentially compressing the tube against the platen surface and thereby causing peristaltic movement of fluid through the tube; characterised by a door that may be opened and closed to allow access to the tube; wherein: the tube is mounted on or in a cassette and the door may be opened to gain access to allow removal of the cassette having the tube thereon or therein and replacement thereof with another cassette having another tube thereon or therein, at least one alignment surface is formed in the door, said alignment surface being configured to register with the cassette when the door is closed, thereby holding the cassette in a desired alignment, and the platen surface is provided on an inner surface of the door and at least one indentation is formed in said platen surface such that the tube will be substantially juxtaposed to the platen surface when the door is closed. the tube is mounted on or in a cassette and the door may be opened to gain access to allow removal of the cassette having the tube thereon or therein and replacement thereof with another cassette having another tube thereon or therein, at least one alignment surface is formed in the door, said alignment surface being configured to register with the cassette when the door is closed, thereby holding the cassette in a desired alignment, and the platen surface is provided on an inner surface of the door and at least one indentation is formed in said platen surface such that the tube will be substantially juxtaposed to the platen surface when the door is closed.