The Gym Challenge set was the fifth and final first generation expansion.Continuing the Gym style from Gym Heroes, Gym Challenge focused more on the Pokémon owned by the gym leaders Sabrina, Koga, Blaine & Giovanni. However, like the other set, it does feature cards from other trainers, in this case; Brock, Misty, Lt. Surge, Erika & Rocket.
This set also introduced the first Pokémon that could do over 100 damage in one attack; Blaine's Arcanine and it also introduced the first card which has three attacks; Rocket's Mewtwo. Several cards also had their artwork edited within this set for western launch. This was due to the pictures potentially causing offence to people who see them.