This book constitutes the refereed proceedings of the 24th International Conference on Conceptual Modeling, ER 2005, held in Klagenfurt, Austria, in October 2005. The 31 revised full papers presented were carefully reviewed and selected from 169 submissions. The papers are organized in topical sections on specific approaches, process modeling and views, conceptual modeling in elearning, managing models and modeling, requirements and software engineering, ontologies, Web services and navigational models, aspects of workflow modeling, queries and OLAP summaries, and temporal and spatial modeling.