October 1999 - Partition theorists argue that when violent ethnic conflict is intense, civil politics cannot be restored unless ethnic groups are demographically separated into defensible enclaves. The empirical evidence suggests otherwise. Some theorists of ethnic conflict argue that the physical separation of warring ethnic groups may be the only possible solution to civil war. Without territorial partition and (if needed) forced population movements, they argue, ethnic war cannot end and genocide is likely. Other scholars have counterargued that partition only replaces internal war with international war, creates undemocratic successor states, and generates tremendous human suffering. So far this debate has been informed by few important case studies. Sambanis uses a new set of data on civil wars to identify the main determinants of ethnic partitions and to estimate their impact on the probability of war's recurrence, on low-grade ethnic violence, and on the political institutions of successor states. Sambanis's analysis is the first large-sample quantitative analysis of the subject, testing the propositions of partition theory and weighing heavily on the side of its critics. He shows that almost all the assertions of partition theorists fail to pass rigorous empirical tests. He finds that, on average, partition does not significantly reduce the probability of new violence. A better strategy might be to combine ethnic groups, but most important is to establish credible and equitable systems of governance. It is also important not to load the strategy with subjective premises about the necessity of ethnically pure states and about the futility of interethnic cooperation. This paper - a product of Public Economics, Development Research Group - is part of a larger effort in the group to study the economics of civil wars. The author may be contacted at nsambanis@worldbank.org.