It would be difficult to overestimate the influence and importance of
modular forms, modular curves, and modular abelian varieties in the
development of num- ber theory and arithmetic geometry during the last
fifty years. These subjects lie at the heart of many past achievements
and future challenges. For example, the theory of complex
multiplication, the classification of rational torsion on el- liptic
curves, the proof of Fermat's Last Theorem, and many results towards the
Birch and Swinnerton-Dyer conjecture all make crucial use of modular
forms and modular curves. A conference was held from July 15 to 18,
2002, at the Centre de Recerca Matematica (Bellaterra, Barcelona) under
the title "Modular Curves and Abelian Varieties". Our conference
presented some of the latest achievements in the theory to a diverse
audience that included both specialists and young researchers. We
emphasized especially the conjectural generalization of the
Shimura-Taniyama conjecture to elliptic curves over number fields other
than the field of rational numbers (elliptic Q-curves) and abelian
varieties of dimension larger than one (abelian varieties of GL2-type).