Empirical studies have measured the effectiveness of decision support systems (DSSs) through a number of variables relating to: (a) the process of decision making or (b) the outcome of such decision making. Few studies have examined effectiveness with both types of variables. Further, empirical studies measuring the effectiveness of DSS have reported equivocal, or even dysfunctional results. This paper examines the relationship between the process and outcomes of decision making through using a DSS. First, it overviews the decision making process, identifies the role of a DSS in improving decision making, and develops a general model of DSS effectiveness. Illustrating with empirical studies, this effectiveness model is used to reconcile the incongruity between the experimental findings and the case—supported theory. The paper concludes with a discussion of the article's implications for information systems research.