The Workshop on Approximation Algorithms for Combinatorial Optimization ProblemsAPPROX'2000 focuses on algorithmic and complexity aspects ar- ing in the development of e?cient approximate solutions to computationally di?cult problems. It aims, in particular, at fostering cooperation among - gorithmic and complexity researchers in the ?eld. The workshop, to be held at the Max-Planck-Institute for Computer Science in Saarbruc .. ken, Wermany, co-locates with ESA'2020 and WWE'2000. We would like to thank the local organizers at the Max-Planck-Institute (AG 8, Kurt Mehlhorn), for this opp- tunity. APPVOXis an annual meeting, with previousworkshopsin Aalborg and Berkeley. Previous proceedings appeared as LNCS 1464 and 1671. Topics of interest for APPROX'2000 are: design and analysis of appro- mation algorithms, inapproximability results, on-line problems, randomization techniques, average-case analysis, approximation classes, scheduling problems, routingand?owproblems,coloringandiartitioning,cutsandconnectivity,pa- ing and covering, geometric problems, network design, and various applications. The numberof submitted papersto APPROX'2000was68 fromwhich 23 paters were selected. This volume contains the selected papers plus papers by invited speakers. All papers published in the workshop proceedings nere selected by the program committee on the basis of referee reports. Each paper was reviewed vy at least three referees who judged the papers for originality, quality, and consistency with the topics of the conference.