This book constitutes the refereed proceedings of the ACM/IFIP/USENIX 9th International Middleware Conference 2008, held in Leuven, Belgium, in December 2008. The 21 revised full papers presented were carefully reviewed and selected from 117 submissions for inclusion in the book. The papers are organized in topical sections on platforms extended to new capabilities, advanced software engineering focusing on specific system properties, system management techniques, as well as components and system algorithms and properties.