The PaCT-2003 (Parallel Computing Technologies) conference was a four-day conference held in Nizhni Novgorod on September 15–19, 2003. This was the 7th international conference of the PaCT series, organized in Russia every odd year. The first conference, PaCT-91, was held in Novosibirsk (Academgorodok), September 7–11, 1991. The next PaCT conferences were held in: Obninsk (near Moscow), 30 August– 4 September, 1993; St. Petersburg, September 12– 15, 1995; Yaroslavl, September 9–12, 1997; Pushkin (near St. Petersburg) September 6– 10, 1999; and Akademgorodok (Novosibirsk), September 3–7, 2001. The PaCT proceedings are published by Springer-Verlag in the LNCS series. PaCT-2003 was jointly organized by the Institute of Computational - thematics and Mathematical Geophysics of the Russian Academy of Sciences (Novosibirsk) and the State University of Nizhni Novgorod. The purpose of the conference was to bring together scientists working with theory, architectures, software, hardware and solutions of large-scale problems in order to provide integrated discussions on Parallel Computing Technologies. The conference attracted about 100 participants from around the world. Authors from 23 countries submitted 78 papers. Of those submitted, 38 papers were selected for the conference as regular ones; there were also 4 invited papers. In addition, a number of posters were presented. All the papers were internationally reviewed by at least three referees. As usual a demo session was organized for the participants. Many thanks to our sponsors: the Russian Academy of Sciences, the Russian Fund for Basic Research, the Russian State Committee of Higher Education, IBM and Intel (Intel laboratory in Nizhni Novgorod) for their—nancial support. The organizers highly appreciate the help of the AssociationAntenne-Provence (France).