Research summary: I add to work that emphasizes the stability of strategic alliances by considering the consequences of alliance partner reconfiguration. I offer two contrasting perspectives: (1) alliance partner reconfiguration leads to disruption, hence increases the risk of subsequent project termination; (2) partner reconfiguration leads to adaptation, hence decreases this risk. Data on 1,025 interfirm Australian mining alliances (2002–2011) shows that on average alliance partner reconfiguration increases the risk of project termination. For firm exit from an alliance, the effect is contingent on a firm's resource base, but not for firm entry. Surprisingly, I do not find that alliance partner reconfiguration is beneficial in a dynamic environment. I discuss the implications of these findings for the literature on strategic alliance dynamics and that on strategic alliance outcomes. Managerial summary: This paper studies what happens when over time strategic alliances change their original membership. The research shows that both entry in and exit from an alliance increase the risk of project termination. Hence, weathering difficult times and managing conflict by keeping teams stable should be a prime directive if project survival is the alliance partners' overriding concern. In addition, I find that the exit of a firm with a comparatively large resource base increases the hazard of termination more than if the departing firm has a relatively small resource base. Therefore, one cannot underestimate the importance of trying to keep on board those alliance partners who bring a critical resource to the table. Copyright © 2015 John Wiley & Sons, Ltd.