Multiple criteria decision making is a major and rapidly growing field of research. Methods resulting from this field of research are used in this book to develop a Multiobjective Decision Support Systems (MODSS) for environmental management. The primary focus of the book is therefore on the issues and practicalities that arise when these methods are applied to support decisions on environmental problems. Most methods included in this book are derived from the literature on multicriteria decision making, decision anlysis and operations research. Concepts developed in management science are used to describe environmental decision processes and to define the functions of decision support. The author's work on MODSS has resulted in the development of a decision support package, called DEFINITE (DEcisions on a FINITE set of alternatives). A demonstration version of this programme is included with the book. This Demo Disk can be run on a MS-DOS compatible personal computer (version 2.0 or higher) having a 3,5 inch, 720 Kb disk drive and 640 Kb available RAM.