In 1996 the International Federation for Information Processing (IFIP) establ- hed its rst Technical Committee on foundations of computer science, TC1. The aim of IFIP TC1 is to support the development of theoretical computer science as a fundamental science and to promote the exploration of fundamental c- cepts, models, theories, and formal systems in order to understand laws, limits, and possibilities of information processing. This volume constitutes the proceedings of the rst IFIP International C- ference on Theoretical Computer Science (IFIP TCS 2000) { Exploring New Frontiers of Theoretical Informatics { organized by IFIP TC1, held at Tohoku University, Sendai, Japan in August 2000. The IFIP TCS 2000 technical program consists of invited talks, contributed talks, and a panel discussion. In conjunction with this program there are two special open lectures by Professors Jan van Leeuwen and Peter D. Mosses. The decision to hold this conference was made by IFIP TC1 in August 1998, and since then IFIP TCS 2000 has bene ted from the e orts of many people; in particular, the TC1 members and the members of the Steering Committee, the Program Committee, and the Organizing Committee of the conference. Our special thanks go to the Program Committee Co-chairs: Track (1): Jan van Leeuwen (U. Utrecht), Osamu Watanabe (Tokyo Inst. Tech.) Track (2): Masami Hagiya (U. Tokyo), Peter D. Mosses (U. Aarhus).