Research in methodology of Decision Support Systems is one of the activities within the System and Decision Sciences Program which was initiated seven years ago and is still in the center of interests of SDS. During these years several methodological approaches and software tools have been developed; among others the DIDAS (Dynamic Interactive Decision Analysis and Support) and SCDAS (Selection Committed Decision Analysis and Support). Both methodologies gained a certain level of popularity and have been successfully applied in other IIASA programs and projects as well as in many scientific institutions. Since development and testing the software and methodologies on real life examples requires certain -- rather high -- resources, it was decided to establish a rather extensive international collaboration with other scientific institutions in various NMO countries. This volume presents the result of the second phase of such a cooperation between the SDS Program and the four scientific institutions in Poland. The research performed during this stage related mostly to converting the decision support software developed during the previous phase, from the mainframe to the microcomputer, ensuring simultaneously high level of rebustness, efficiency and user friendliness. Several new theoretical developments, like new non-simplex algorithm for linear programming, new algorithms for mixed-integer programming and job shop scheduling are also described in the volume. Finally, it presents also new theoretical developments relating to supporting the processes of negotiations as well as the methodological issues on application the Decision Support Systems in industry management.