Still today I am receiving requests for reprints of the book, but unfortunately it is out of print. Therefore, since the book still seems to receive some attention, I p- posed to Springer Verlag to provide a free online edition. I am very happy that Springer agreed. Except for the correction of some typographical errors, the online edition is just a copy of the printed version, no updates have been made. In particular, Table 13.1 gives the status of TSPLIB at the time of publishing the book. For accessing TSPLIB the link http: //www.iwr.uni-heidelberg.de/iwr/comopt/software/TSPLIB95/ should be used instead of following the procedure described in Chapter 13. Heidelberg, January 2001 Gerhard Reinelt Preface More than ?fteen years ago, I was faced with the following problem in an assignment for a class in computer science. A brewery had to deliver beer to ?ve stores, and the task was to write a computer program for determining the shortest route for the truck driver to visit all stores and return to the brewery. All my attemps to ?nd a reasonable algorithm failed, I could not help enumerating all possible routes and then select the best one.