When Scott Summers developed his mutant eye beams, he trained himself to operate blind, fearful of the damage he could cause with his powers. He dated Lorna Dane, a fellow mutant with magnetic powers, until she dumped him for his older brother, Alex. Later, Scott was rescued from a lynch mob by the telepath Charles Xavier, who recruited him to be the first X-Man, Cyclops. Alex turned down a similar invitation. Scott fell in love with Jean Grey (Marvel Girl), Xavier's next recruit, but hesitated to tell her. After the X-Men rescued the President's kidnapped daughter, Cyclops became disillusioned, allegedly because of Xavier's dealings with an anti-mutant U.S. administration, but also because Jean had become involved with new recruit Wolverine. Scott defected to the terrorist Brotherhood of Mutants. When their leader, Magneto, set out to annihilate Washington, Cyclops rejoined the X-Men, even convincing Magneto's son Quicksilver to help defeat him.

When teammate Colossus quit and returned to Russia, Cyclops and Marvel Girl followed and convinced him to rejoin; during this period Scott and Jean grew closer, and soon after, became an item. Though his relationship with Jean had already ended, a jealous Wolverine fought with Scott. Xavier tried to force them to learn to co-exist, sending them on a mission to the Savage Land to find missing U.S. marines. They faced a sentient computer and its army of cyborg zombies; while fleeing a collapsing underground complex, Wolverine deliberately let Cyclops fall in to a chasm. Cyclops survived the fall, albeit severely injured, and clung to life by eating grubs and worms to survive. After twenty-six days he was found by Brotherhood members, who failed to recognize him as "the traitor Cyclops", and took him back to their new base, the Citadel, for medical treatment. When Magneto plotted to reverse Earth's magnetic fields, Cyclops summoned in the X-Men in time to stop him. After the battle, Cyclops confronted a penitent Wolverine and violently removed him from the team. Months later, Cyclops reconsidered and invited Wolverine back, feeling it was his best chance to rehabilitate.

Scott was reunited with his estranged brother Alex, who joined Emma Frost's rival mutant educational program, The Academy of Tomorrow. They failed to resolve their differences. Later, when Lorna, now called Polaris, apparently lost control of her powers and killed several people, Cyclops tried to prevent Alex and other Frost students from breaking into the Triskelion to rescue her.