| 1 | X-Men (1st series) | 1st appearance of X-Men; 1st appearance of Magneto; 1st appearance of Professor X; 1st appearance of Angel (Warren Worthington III); 1st appearance of Beast (Hank McCoy); 1st appearance of Cyclops (Scott Summers); 1st appearance of Iceman (Bobby Drake); 1st appearance of Marvel Girl (Jean Grey); Origin of X-Men |
| 1-2 | X-Men (1st Series) | 1st appearance of Iceman (Bobby Drake); 1st appearance of Magneto; 1st appearance of Marvel Girl (Jean Grey); 1st appearance of Professor X; 1st appearance of X-Men; Origin of X-Men; Kevin Dooley LOC; St appearance of Cyclops (Scott Summers) |
| 1/A | X-Men (1st Series) | 1st appearance of Angel (Warren Worthington III); 1st appearance of Beast (Hank McCoy); 1st appearance of Cyclops (Scott Summers); 1st appearance of Iceman (Bobby Drake); 1st appearance of Magneto; 1st appearance of Marvel Girl (Jean Grey); 1st appearance of Professor X; 1st appearance of X-Men; Origin of X-Men; Kevin Dooley LOC |
| 1/B | X-Men (1st Series) | 1st appearance of Angel (Warren Worthington III); 1st appearance of Beast (Hank McCoy); 1st appearance of Cyclops (Scott Summers); 1st appearance of Iceman (Bobby Drake); 1st appearance of Magneto; 1st appearance of Marvel Girl (Jean Grey); 1st appearance of Professor X; 1st appearance of X-Men; Origin of X-Men; Kevin Dooley LOC |
| 1/C | X-Men (1st Series) | 1st appearance of Angel (Warren Worthington III); 1st appearance of Beast (Hank McCoy); 1st appearance of Cyclops (Scott Summers); 1st appearance of Iceman (Bobby Drake); 1st appearance of Magneto; 1st appearance of Marvel Girl (Jean Grey); 1st appearance of Professor X; 1st appearance of X-Men; Origin of X-Men; Kevin Dooley LOC |
| 1/D | X-Men (1st Series) | Origin of X-Men; 1st Appearance of Professor X; 1st Appearance of X-Men; 1st Appearance of Angel (Warren Worthington III); 1st Appearance of Beast (Hank McCoy); 1st Appearance of Cyclops (Scott Summers); 1st Appearance of Iceman (Bobby Drake); 1st Appearance of Marvel Girl (Jean Grey); 1st Appearance of Magneto |
| 1/E | X-Men (1st Series) | 1st appearance of Iceman (Bobby Drake); 1st appearance of Magneto; 1st appearance of Marvel Girl (Jean Grey); 1st appearance of Professor X; 1st appearance of X-Men; Origin of X-Men; Kevin Dooley LOC; St appearance of Cyclops (Scott Summers) |
| 1 | X-Men (UK Edition) | 1st appearance of Angel (Warren Worthington III); 1st appearance of Beast (Hank McCoy); 1st appearance of Cyclops (Scott Summers); 1st appearance of Iceman (Bobby Drake); 1st appearance of Magneto; 1st appearance of Marvel Girl (Jean Grey); 1st appearance of Professor X; 1st appearance of X-Men; Origin of X-Men |