This book constitutes the refereed proceedings of the 13th European PVM/MPI Users' Group Meeting, held in September 2006. The book presents 38 revised full papers together with abstracts of 6 invited contributions, 4 tutorial papers and 6 poster papers. The papers are organized in topical sections on collective communication, communication protocols, debugging and verification, fault tolerance, metacomputing and grid, parallel I/O, implementation issues, object-oriented message passing, limitations and extensions and performance.