The authors' original motivation for the book was a one-semester course on network optimization for senior masters' level classes of econometrics and operations research. The textbook is suitable for a 'middle level' course for a student of econometrics or operations research interested not only in reading about network optimization theory, but also providing first-hand experience in solving and analyzing reasonably sized programs with computer software. Networks in Action: Text and Computer Exercises in Network Optimization should spark students' interest in modeling problems as networks, to sensitize them to the fact that elegant and effective solution methods are available once a problem gets modeled as a network, and to guide them to use computer based software tools to solve these problems. Every chapter ends with a brief description of additional exercises that are left unsolved in order to show students that the problems covered in each of the chapters are not the only problems with which network optimization deals. TOC:The Modeling and Implementing Process.- Network Theory.- References with Comments.- Shortest Paths.- Minimum Spanning Trees.- Network Flows.- Matchings.- Facility Location.- Cyclic Routing on Networks. One of the most well-known of all network optimization problems is the shortest path problem, where a shortest connection between two locations in a road network is to be found. Networks occur in an extremely wide range of applications, among them are: road networks;