Apparatus for admitting sheets of unexposed X-ray film into and for removing sheets of exposed X-ray film from cassettes of the type having two pivotally connected sections which are separably locked to each other has a housing with a wall which is pivotable to and from an open position in which a cassette containing a sheet of exposed film is inserted into the housing so that one of its sections lies against a pivotable partition while the latter assumes a first position to thereby seal a cassette-receiving first compartment from a second compartment of the housing. A mechanism is actuated in the closed position of the wall to unlock the cassette in the first compartment and to hold the other section of such cassette against movement with the partition. The partition is thereupon pivoted to a lowermost position, together with the one section of the cassette, so that the exposed sheet can descend by gravity into a tray in the second compartment. On its way back to the first position, the partition moves the one section into the range of a suction head which transfers an unexposed sheet from a tray in the second compartment into the space between the two sections. The cassette is locked and its other section detached from the mechanism when the partition returns to its first position, and the locked cassette is removed from the first compartment on movement of the wall to open position.