Magnetic tape cassette loading system in recording and/or reproducing apparatus

A magnetic tape cassette loading system for a recording and/or reproducing apparatus, includes a cassette holder assembly (24) for receiving and holding one cassette of any of a number of different sizes (C1 to C3). The cassette holder assembly includes an outer cassette holder (60) which is moveable within the loading system body in the vertical and horizontal directions, and an inner cassette holder (58) which supports a cassette therein and which is so supported on the outer cassette holder as to be movable thereon in the horizontal direction. The inner and outer cassette holders are cooperable to cause a cassette to move to an eject position, in which a cassette can be received into the cassette holder assembly and removed therefrom, and a loaded position in which cassette loading is completed. The cassette loading system also includes a cassette guiding mechanism for guiding a cassette to the cassette holder assembly so as to position the cassette in the cassette holder assembly at a predetermined position adapted to each of the different sized cassettes. The cassette guiding mechanism includes stopper members which prevent a cassette from being received and held in the cassette holder assembly at a position other than the predetermined position and/or from being obliquely introduced into the cassette holder assembly.