For the past 25 years the CADE conference has been the major forum for the presentation of new results in automated deduction. This volume contains the papers and system descriptions selected for the 17th International Conference on Automated Deduction, CADE-17, held June 17-20, 2000, at Carnegie Mellon University, Pittsburgh, Pennsylvania (USA). Fifty-three research papers and twenty system descriptions were submitted by researchers from ?fteen countries. Each submission was reviewed by at least three reviewers. Twenty-four research papers and ?fteen system descriptions were accepted. The accepted papers cover a variety of topics related to t- orem proving and its applications such as proof carrying code, cryptographic protocol veri?cation, model checking, cooperating decision procedures, program veri?cation, and resolution theorem proving. The program also included three invited lectures: "High-level veri?cation using theorem proving and formalized mathematics" by John Harrison, "Sc- able Knowledge Representation and Reasoning Systems" by Henry Kautz, and "Connecting Bits with Floating-Point Numbers: Model Checking and Theorem Proving in Practice" by Carl Seger. Abstracts or full papers of these talks are included in this volume.In addition to the accepted papers, system descriptions, andinvited talks, this volumecontains one page summaries of four tutorials and ?ve workshops held in conjunction with CADE-17.

This volume contains the papers presented at the Sixth International Conference on Logic for Programming and Automated Reasoning (LPAR'99), held in Tbilisi, Georgia, September 6-10, 1999, and hosted by the University of Tbilisi. Forty-four papers were submitted to LPAR'99. Each of the submissions was reviewed by three program committee members and an electronic program com mittee meeting was held via the Internet. Twenty-three papers were accepted. We would like to thank the many people who have made LPAR'99 possible. We are grateful to the following groups and individuals: to the program committee and the additional referees for reviewing the papers in a very short time, to the organizing committee, and to the local organizers of the INTAS workshop in Tbilisi in April 1994 (Khimuri Rukhaia, Konstantin Pkhakadze, and Gela Chankvetadze). And last but not least, we would like to thank Konstantin - rovin, who maintained the program committee Web page; Uwe Waldmann, who supplied macros for these proceedings and helped us to install some programs for the electronic management of the program committee work; and Bill McCune, who implemented these programs."