Legacy information systems consume a large portion of information technology budgets and often impose serious limitations on organizations’ flexibility and innovation. Despite the extensive literature on how organizations adopt and use new IS, we know little about how organizations discontinue their legacy IS. Current studies suggest some actions and events to cease mechanisms such as legitimization, learning, and routinization that give continuity to the systems. However, we do not know when these actions emerge in the discontinuance process to gradually reduce the organizational commitments to legacy IS, nor do we know how ceasing one mechanism can facilitate or, conversely, hamper ceasing other mechanisms, especially when these systems involve interdependences between various components. Based on a process analysis of four software companies, we show that, contrary to the current literature, IS discontinuance is not a matter of merely ceasing each and every mechanism of an established IS; rather, it often requires that some mechanisms be temporarily intensified to prevent premature discontinuance and enable subsequent cessation of other mechanisms. Through cross-case analysis, we articulate a set of causal mechanisms that expands our understanding of how the discontinuance process can be differently shaped by organizational commitments and interdependences involved in legacy IS.