Computational Science is becoming a vital part of many scienti?c investi- tions, impacting researchers and practitioners in areas ranging from aerospace andautomotiveto chemistry,electronics,geosciences,?nance,mathematics,and physics. Due to the sheer size of many challenges in computational science, the use of supercomputing, parallel processing, and sophisticated algorithms is - evitable. This volume contains the proceedings of The 2003 International Conference on Computational Science and Its Applications (ICCSA 2003), held in M- treal, Canada in May 2003. The papers presented here re?ect the aim of the programcommittee to bring together researchersand scientists from mathem- ics and computer science, the basic computing disciplines, and researchers from various application areas who are pioneering advanced application of compu- tional methods to sciences such as physics, chemistry, life sciences, engineering, arts, and the humanities, along with software developers and vendors, to d- cuss problems and solutions in the area, identify new issues, and shape future directions for research, as well as help industrial users apply various advanced computational techniques. Our outstanding invited speakers outlined the theme for the Conference, consideringsophisticatednumericalcomputationalmethods,emergingcompu- tional solutions, and problems and applications pushing the bounds of advanced computing techniques and hardware. This Conference was held as the ?rst in its series, with an emphasis on C- putational Science and the application of computational science. Interest from researchers and practitioners in this interdisciplinary area has been overwhe- ing, and we are looking forward to future events in this Conference series.