This yearmarks anexciting time in the XML-database space: XQueryis moving closer to becoming a full W3C Recommendation, and the "Big 3" database vendors (IBM, Oracle, Microsoft) are expected to release XQuery support in theirrelationalDBMSs, joininganumberofexistingopensourceandcommercial products. Thus, we are very pleased to feature an industrial paper (describing theXML-speci?cfeaturesofMicrosoftSQLServer)aswellas14researchpapers. XSym's focus this year was on building XML repositories, and papers discussed the following topics: indexing support for the evaluation of XPath and XQuery; benchmarks and algorithms for XQuery and XPath evaluation; algorithms for constraint satisfaction checking, information extraction, and subtree matching; and applications of XML in information systems. This year, XSym also coordinated its e?orts with the Database and P- gramming Languages Symposium, DBPL 2005. The resulting program included not only presentations of the papers in this proceedings, but also a joint DBPL- XSym keynote talk by Giuseppe Castagna, developer of the CDuce language for XML processing, and a joint panel on open XML research problems and challenges. The organizers would like to express their gratitude to the XSym Program Committee and external reviewers for their e?orts in providing very thorough evaluationsofthesubmittedpapersundersigni?canttimeconstraintsandto- crosoftfortheirsponsorshipandfortheuseoftheMicrosoftConferenceMana- ment Toolkit. We would also like to thank Gavin Bierman and Christoph Koch, the organizersof DBPL, for their e?orts andtheir willingness to coordinate with us. These proceedings are dedicated to Alberto Mendelzon who sadly passed awaythisyear.Asastrongsupporterofandactivecontributortothissymposium series he will always remain in our memory.