During the past two decades, the world has witnessed a demographic epidemic of unprecedented proportions-an epidemic of forced migrations that has had grave public-health consequences. These mass migrations have in large part resulted from wars, civil strife and violence that have plagued so many parts of the developing world. Now, in the 1990s, the same phenomena have returned to Europe; ethnic-based wars have generated millions of refugees and internally displaced persons in the former Yugoslavia, Chechnya, Armenia, Azerbaijan and Georgia. In this paper, I will summarize our knowledge of the public-health impact of mass population displacement; look at the essential elements of an effective public health response to emergencies involving refugee and displaced populations; and attempt to analyze the reasons for the relative failure of the international community to act decisively and consistently to prevent the most serious adverse consequences of these crises for the affected populations.