Middleware 2004, the ACM/IFIP/Usenix 5th International Middleware Conference, covers middleware research and technology. The conference focuses broadly on the design, implementation, deployment, and evaluation of distributed systems platforms and architectures for future computing environments. One of the planned workshops, iMiddleware for Pervasive and Ad-Hoc Computing, seeks to develop a road map for research on essential software infrastructures for ad hoc and pervasive computing. The workshop identifies appropriate core architectures, languages and systems to address the specific problems of large-scale, real-world, pervasive computing environments.