The 5th International Symposium on High Performance Computing (ISHPC–V) was held in Odaiba, Tokyo, Japan, October 20–22, 2003. The symposium was thoughtfully planned, organized, and supported by the ISHPC Organizing C- mittee and its collaborating organizations. The ISHPC-V program included two keynote speeches, several invited talks, two panel discussions, and technical sessions covering theoretical and applied research topics in high–performance computing and representing both academia and industry. One of the regular sessions highlighted the research results of the ITBL project (IT–based research laboratory, http://www.itbl.riken.go.jp/). ITBL is a Japanese national project started in 2001 with the objective of re- izing a virtual joint research environment using information technology. ITBL aims to connect 100 supercomputers located in main Japanese scienti?c research laboratories via high–speed networks. A total of 58 technical contributions from 11 countries were submitted to ISHPC-V. Each paper received at least three peer reviews. After a thorough evaluation process, the program committee selected 14 regular (12-page) papers for presentation at the symposium. In addition, several other papers with fav- able reviews were recommended for a poster session presentation. They are also included in the proceedings as short (8-page) papers. Theprogramcommitteegaveadistinguishedpaperawardandabeststudent paper award to two of the regular papers. The distinguished paper award was given for “Code and Data Transformations for Improving Shared Cache P- formance on SMT Processors” by Dimitrios S. Nikolopoulos. The best student paper award was given for “Improving Memory Latency Aware Fetch Policies for SMT Processors” by Francisco J. Cazorla.