ISBA 2004 aims at promoting the development of Bayesian Statistics from a theoretical and methodological viewpoints as well as applications in as many fields as possible. S pecial emphasis is given to the role played by Bayesian Statistics in a world where the multidisciplinary activity has grown enormously over the last decade. The organizers are also particularly interested in stimulating the participation of young researchers, students, Latin-American researchers and professionals in general as well as their interaction with Bayesian statisticians. Having this in mind the Scientific Program includes debates over fundamental issues in Bayesian Statistics, basic and advanced level tutorials, sessions discussing methods, theory, educational aspects, applications in a wide range of fields, and the always popular poster sessions.