This volume contains the Proceedings of the "2hme Colloque International d'Algibre et Thiorie des Nombres," organized in November 2001 by the Faculti des Sciences et Techniques de Fhs, in collaboration with the Faculti des Sciences de Fhs. The organizing committee consisted of F. Ezzaki, H. Ziat, L. Oukhtit, A. El Baraka, and I. Akharraz, while the scienti.c assistance was assured by J.-P. Tignol (Universiti Catholique de Louvain), S. Caenepeel (Vrije Universiteit Brussel), M. Boulagouaz (Faculti des Sciences et Techniques de Fhs), and M. Charkani (Faculti des Sciences de Fhs). All papers in this volume have been refereed individually.