This book constitutes the refereed proceedings of the 5th Annual International Conference on Computing and Combinatorics, COCOON'99, held in Tokyo, Japan in July 1999. The 46 revised papers presented were carefully reviewed and selected from a total of 88 submissions; also included are two invited survey papers. The papers are organized in topical sections on data structures, computational biology, graph drawing, discrete mathematics, graph algorithms, automata and languages, complexity theory and learning, combinatorial optimization, number theory, distributed computing, network routing, computational geometry, online algorithms, rewriting systems, and parallel computing.