Although the global incidence of violent conflict seems to be in decline, the prevailing feeling is that the international community’s efforts to address armed conflicts leave a lot to be desired. The results of recent interventions, from Kuwait to Bosnia and Kosovo, have been mixed at best. At the rhetorical level, the international community has learned one major lesson: that prevention is far wiser and cheaper than intervention. The case for preventive action rests not only on moral imperative but also on hard cost–benefit calculations: early preventive action is more likely to succeed than later interventions because the stakes are lower and the chances of success greater. Conflict prevention has become a new mantra in both the conflict management and the development communities. But can it ever be more than that? This article examines the case for prevention, questioning whether it will ever be possible to move from rhetoric to reality, and describes three particular challenges facing the United Nations in its efforts.