Thepapersinthis volumewerepresentedatthe4thInternationalConferenceon Large-Scale Scienti?c Computations ICLSSC 2003. It was held in Sozopol, B- garia, June 4-8, 2003. The conference was organized and sponsored by the C- tral Laboratory for Parallel Processing at the Bulgarian Academy of Sciences. Support was also provided from the Center of Excellence "BIS 21" (funded by the European Commission), SIAM and GAMM. A co-organizer of this tra- tional scienti?c meeting was the Division of Numerical Analysis and Statistics of the University of Rousse. The success of the conference and the present volume in particular are the outcome of the joint e?orts of many colleagues from various institutions and organizations. First thanks to all the members of the Scienti?c Committee for their valuable contribution to forming the scienti?c face of the conference, as well as for their help in reviewing contributed papers. We would like to specially thank the organizers of the special sessions: R. Blaheta, N. Dimitrova, A. Ebel, K. Georgiev, O. Iliev, A. Karaivanova, H. Kosina, M. Krastanov, U. Langer, P. Minev, M. Neytcheva, M. Sch. afer, V. Veliov, and Z. Zlatev. We are also grateful to the sta? involved in the local organization. Special Events: - The conference was devoted to the 60th anniversary of Raytcho Lazarov. - During the conference, the nomination for the World Level of the Hall of Fame for Engineering, Science and Technology, HOFEST, was o?cially awarded to Owe Axelsson.