This volume constitutes the proceedings of the Fourth International Conference on Multi-objective Progranuning and Goal Programming. Theory & Applications (MOPGP'OO) held in Ustron, Poland on May 29 - June 1,2000. Sixty six people from 15 countries attended the conference and 53 papers were presented. MOPGP'OO was organized by the Department of Operations Research, The Karol Adamiecki University of Economics in Katowice, Poland and chaired by Tadeusz Trzaskalik. The members of the International Committee were: James Ignizio, Dylan Jones, Pekka Korhonen, Carlos Romero, Ralph Steuer and Mehrdad Tamiz. The Local Organizing Committee consisted of Ewa Konarzewska-Gubala, Ignacy Kaliszewski, Jaroslav Ramik, Andrzej Skulimowski, Roman Slowinski and Tadeusz Trzaskalik. The volume is divided into two parts: Theory and Applications. 15 papers from Part direct at theoretical topics, in Part II there are 18 papers on innovative applications, implementation and practice of multi-objective programming and goal progranuning. Thanks to the efforts made by the referees, readers will enjoy turning the pages. MOPGP'OO was made possible by the support of the State Committee for Scientific Research (KBN) and The Karol Adamiecki University of Economics in Katowice. I would like to thank to the all people who helped to organize the conference, have made the success of MOPGP'OO possible.