This volume contains expanded versions of lectures given at an instruc tional conference on number theory and arithmetic geometry held August 9 through 18, 1995 at Boston University. Contributor's include The pu rpose of the conference, and of this book, is to introduce and explain the many ideas and techniques used by Wiles in his proof that every ( semi-stable) elliptic curve over Q is modular, and to explain how Wile sF result can be combined with Ribet's theorem and ideas of Frey and S erre to show, at long last, that Fermat's Last Theorem is true.