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...