Abstract: A portable microfilm viewer for viewing a microfilm contained in a cassette. The viewer includes a housing with a lens system mounted therein. The cassette is removably received on a film transport mechanism which both supports and drives the film. A source of rotary motion is fixedly mounted on the housing and a bidirectional engaging device couples the rotary output to the film transport means for selectively transporting the film of the cassette in either of two directions across the lens system. The source of rotary motion can be a manual wheel or a motor device. A counter can be included for determining the film frame being viewed and for setting a desired film frame to be viewed, whereby the device will automatically stop when the desired film frame is in view. In an embodiment of the invention the microfilm viewer can also accommodate microfiche cards which can be viewed through the same lens system.