Bio Rider! (バイオライダー！ Baio Raidā!) is the seventeenth episode of Kamen Rider Black RX. It's the fourth and final part of a four episode story arc. It features the debut appearance of RX's second alternate form, Bio Rider, following Robo Rider which first appeared two episodes previously. Bio Rider's debut is accompanied by the introduction of its corresponding Acrobatter form, Mach Jabber. The Sahara Kids also learn that Kohtaro is RX in this episode.