The ?rst International Symposium on the Applications of Constraint Databases (CDB2004) took place in Paris, France, on June 12–13, 2004, just before the ACM SIGMOD and PODS conferences. Since the publication of the paper “Constraint Query Languages” by Kan- lakis, Kuper and Revesz in 1990, the last decade has seen a growing interest in constraint database theory, query evaluation, and applications, re?ected in a variety of conferences, journals, and books. Constraint databases have proven to be extremely ?exible and adoptable in environments that relational database systems cannot serve well, such as geographic information systems and bioinf- matics. This symposium brought together people from several diverse areas all c- tributing to the practice and the application of constraint databases. It was a continuation and extension of previous workshops held in Friedrichshafen, G- many (1995), Cambridge, USA (1996), Delphi, Greece (1997), and Seattle, USA (1998) as well as of the work in the comprehensive volume “Constraint Data- ses” edited by G. Kuper, L. Libkin and J. Paredaens (2000) and the textbook “Introduction to Constraint Databases” by P. Revesz (2002). The aim of the symposium was to open new and future directions in c- straint database research; to address constraints over domains other than the reals; to contribute to a better implementation of constraint database systems, in particular of query evaluation; to address e?cient quanti?er elimination; and to describe applications of constraint databases.