This book constitutes the refereed proceedings of the 25th International Conference on Conceptual Modeling, ER 2006, held in Tucson, AZ, USA in November 2006.

The 37 revised full papers presented together with 2 keynote talks, 2 panel session papers, 6 industrial papers, and 5 demo/posters papers were carefully reviewed and selected from 158 submissions. The papers are organized in topical sections on Web services, quality in conceptual modeling, aspects of conceptual modeling, modeling advanced applications, XML, semantic Web, requirements modeling, aspects of interoperability, metadata management, human-computer interaction, business modeling, and reasoning.