This book constitutes the thoroughly refereed post-proceedings of the Third International Workshop on the World Wide Web and Databases, WebDB 2000, held in Dallas, Texas, USA in May 2000. The 16 revised full papers presented together with one invited papers were carefully reviewed and selected after two rounds of reviewing and revision from a total of 69 initial submissions. The papers are organized in topical sections on information gathering, caching, querying in XML, XML structuring and versioning, web modling, query processing, and classification and retrieval.