The papers in this volume were selected for presentation at the 6th Annual International Computing and Combinatorics Conference (COCOON2000), in Sydney, Australia from July 26 - 28, 2000. The topics cover many areas in t- oretical computer science and combinatorial optimization. There were 81 high quality papers submitted to COCOON2000. Each paper was reviewed by at least three program committee members, and the 44 papers were selected. It is expected that most of them will appear in a more complete form in scientic journals. In addition to the selected papers, the volume also contains the papers from two invited keynote speeches by Christos Papad- itriou and Richard Brent. This year the Hao Wang Award was given to honor the paper judged by the programcommittee to have the greatest merit. The recipient is \Approximating Uniform TriangularMeshes in Polygons"byFranz Aurenhammer, NaokiKatoh, Hiromichi Kojima, Makoto Ohsaki, and Yinfeng Xu. The rst Best Young - searcher paper award was given to William Duckworth for his paper \Maximum Induced Matchings of Random Cubic Graphs". We wish to thank all who have made this meeting possible: the authors for submitting papers, the program committee members and the external referees, sponsors, the local organizers, ACM SIGACT for handling electronic subm- sions, Springer-Verlagfor their support, and Debbie Hatherellfor her assistance.