This book constitutes the refereed proceedings of the 4th International Conference on Mobile Data Management, MDM 2003, held in Melbourne, Australia, in January 2003. The 21 revised full papers and 15 revised short papers presented were carefully reviewed and selected from 87 submissions. The papers are organized in topical sections on storage management, location tracking, information management, location-aware services, context-aware services, resource discovery, location management, storage management and query processing, and context-aware information services.