A sterilization and storage cassette formed of heat-resistant plastic and having two identical tray halves. In one embodiment, at least one tray half includes a rotatable retaining member for retaining dental instruments within the tray. In a second embodiment, a clamping member is inserted in one tray and at least one and preferably a plurality of instrument supports is inserted into the other tray. When the trays are closed together, the clamping member presses down upon and retains dental instruments placed on the supports. The trays are detachably connected through a hinge mechanism. Each tray has separate, distinct hinge members on one of its sides, and a set of separate, distinct latch members on another of its sides.