First appearance of James Proudstar, the second Thunderbird. First team appearance of the Hellions: Roulette, Empath, Jetstream, Tarot, Thunderbird, Cat's Eye.
ACE edition reprint produced by Wizard. Acetate cover. Second team appearance of the X-Men that debuted in Giant-Size X-Men #1. Second appearance of Storm, Nightcrawler, Colossus, Thunderbird. Fourth appearance of Wolverine.
Marvel Milestones Edition reprint. First appearance of Storm, Nightcrawler, Colossus, Thunderbird. First appearance of Illyana Rasputin as a child. First appearance of Krakoa. Second appearance of Wolverine. First use of "snikt" sound effect.