A cartridge for housing a disk-shaped information recording medium to be inserted in a recording and reproduction apparatus. The cartridge includes a first case for enclosing a first half of the disk and a second case for enclosing a second half of the disk. The first and second cases are movable into and out of contact with each other along a pair of disk support members. When the first and second cases are in contact with each other the disk is completely enclosed and protected from contamination. Upon insertion in the recording and reproduction apparatus, the first and second cases are automatically separated by a predetermined distance to expose a radial portion of the disk for recording and reproduction.