In the “quest” (Delone and McLean 1992) for reliable and practical measures of IS success, a growing stream of research has argued that a key predictor of performance impacts is user evaluations of fit between task requirements and characteristics of the system or technology (Goodhue and Thompson 1995; Vessey and Galletta 1991; Jarvenpaa 1989; Goodhue 1988). The argument is that a better fit produces better performance — good fit is desirable. It has also been argued that users are quite capable of reliably evaluating fit (Goodhue 1995). While both intuitively and empirically there is some support for these notions, evidence presented in this research suggests that users can misperceive their fit with technology. Furthermore, it is argued that such misperceptions of fit can inhibit learning and productivity with technology (generativity), and at the extreme may lead to catastrophic decision making by users (Weick 1990). The basis for these arguments draws on work in ecological psychology, cognitive science, and organizational theory to identify four types of fit, and focuses particularly on the process dynamics of how fit emerges from user-technology interactions.