In recent years, the need for a review of the state of the art in Combinatorial Optimization has been felt by many scientists and researchers in the field. The opportunity of achieving this aim was offered by the Deputy Secretary General of the International Centre of Mechanical Sciences, Professor A. Marzollo, who invited the contributors of this volume to Udine for a Workshop. During the meeting the participants discussed their results and their ideas on the future developments of the various facets of this expanding area of applied mathematics. The success of the Workshop and the encouragement of the participants suggested that I collect the main contributions in the present volume. It is my hope that it may both give a sound background to people entering this fascinating area of study and stimulate further research in the field. The Editor Sergio Rinaldi LIST OF CONTRIBUTORS BARTHES, J. P.: Departement d'informatique et de Mathematiques Appli- quees - Universite de Technologie de Compiegne - 60200 Compiegne, France. LAWLER, E. L.: Dept. of Electrical Engineering and Computer Science - University of California at Berkeley - U. S. A. LUCCIO, F.: Universita di Pisa - Pisa - Italy. MAFFIOLI, F.: Istituto di Elettrotecnica ed Elettronica and Centro di Telecomuni- cazioni Spaziali of C. N. R. - Politecnico di Milano - Milano - Italy. MARTELLI, A.: Istituto di Elaborazione dell'Informazione del C. N. R. - Via S. Maria, 46 - Pisa - Italy.