This book constitutes the refereed proceedings of the 13th International Conference on Integer Programming and Combinatorial Optimization, IPCO 2008, held in Bertinoro, Italy, in May 2008. The 32 revised full papers presented were carefully reviewed and selected from 95 submissions. The papers cover various aspects of integer programming and combinatorial optimization and present recent developments in theory, computation, and applications in that area. Topics included are such as approximation algorithms, branch and bound algorithms, branch and cut algorithms, computational biology, computational complexity, computational geometry, cutting plane algorithms, diophantine equations, geometry of numbers, graph and network algorithms, integer programming, matroids and submodular functions, on-line algorithms and competitive analysis, polyhedral combinatorics, randomized algorithms, random graphs, scheduling theory and scheduling algorithms, and semidefinite programs.