From the inside front endpaper:
A NOTE ON THE SECOND PRINTING
This the second printing of Mutant: Year Zero. The book remains essentially the same, but a few typos and errors have been fixed. In addition, some minor rules updates have been made: Opposed rolls have been added (page 48), affecting the Sneak (page 50), Scout (page 51) and Manipulate (page 53) skills. Also, the Dog Handler’s talents (page 64), the initiative rules (page 79), the rules for armor (page 88), and for recovery of Strength and Agility (page 90) have been updated.