Humanitarian relief operations into complex emergencies in the post_Cold War era face many challenges. One of these is understanding and mitigating the possible adverse effects of humanitarian aid on target conflicts and populations. Humanitarian relief efforts can prolong, exacerbate, or in other ways harm the progression of emergency_causing conflicts. Moreover, relief operations sometime undermine the development prospects of the target population, which is essential for reducing a population's vulnerability to future emergencies. This essay reviews the literature on this topic and offers some direction for future research.