This book constitutes the refereed proceedings of the 9th East European Conference on Advances in Databases and Information Systems, ADBIS 2005, held in Tallinn, Estonia, in September 2005.

The 27 revised full papers presented together with an invited paper were carefully reviewed and selected from 144 submissions. The papers are organized in topical sections on database theory, database modelling and physical database design, query processing, heterogeneous databases and interoperability, XML and databases, data mining and knowledge discovery, information systems and software engineering, and information systems development.