This paper presents the results of a research concerning the type, category and fields of applications of Decision Support Systems (DSS) and their contribution to decision-making in agriculture, mainly in the fields of planning and management of farms, farm regions and agricultural resources. More specifically, the paper includes a taxonomy survey that has been based on an analysis of all published works on applications of DSS from 1987 to 2001, as well as a categorized presentation of these applications. The relevant classification of DSS is made by treating subject (theoretical DSS or applicative), the source of publication (proceedings, scientific journal or dissertation), the type of DSS (Decision Support System, Expert System or Knowledge Based DSS), the operational research model that each one DSS uses, the operational field (Diagnostic Forecasting, Advisory, Control, Educational Informational, Operational), the category of decisions (Strategic or Tactic planning decision) and the year of application. The basic concepts and characteristics of DSSs along with the important role that they play in the decision-making process in agriculture, are also described at the beginning of this paper.