Since 1990, the republic of Guinea (2000 population: 7.5 million) has accepted 390,000-450,000 refugees from Sierra Leone and Liberia. During this 10-year period, refugees have lived in small villages scattered throughout rural southeastern Guinea. During September-December 2000, attacks by armed factions in Guinea led to the widespread displacement of refugees living in the southeastern camps; the refugees subsequently were transferred to safer camps in the northwest. Approximately 280,000 refugees initially were estimated to have been displaced. After the attacks, the number of refugees relocated was approximately 58,000. This report demonstrates methods used to calculate mortality rates when large populations are displaced. The findings indicate that the number of refugees in Guinea before the relocation probably was overestimated. The mortality rates calculated using conservative denominator numbers did not meet the definition of an emergency phase of a complex emergency, and mortality rates were lower for refugees compared with baseline rates for the local population. Accurate methods are needed to estimate population size in complex emergencies to provide resources to vulnerable groups.