Abstract: A thermal transfer ribbon cassette system for use with a thermal transfer printer comprises supply and take-up spools, a thermal transfer ribbon extending between the spools with one end loaded onto the supply spool and the other onto the take-up spool, a cassette casing (10) with spool-locating means (15, 16) to locate and retain the two ribbon-carrying spools (5) spaced-apart, parallel and rotatable during printing, the spacing between the spools being predetermined to fit the printer, and a disposable loading member (20) comprising a rigid body portion (21) shaped to be manually transportable and having spool-holding means (23) releasably to hold the loaded spools (5) parallel, non-rotatable and spaced apart with the same predetermined spacing as the spool-locating means (15, 16); the spools (5), casing (10) and loading member (20) being adapted to enable the spools (5) to be inserted into the spool-locating means (15, 16) of the casing (10) while being held by the loading member (20), and to enable the lo