More than 30 million refugees and internally displaced persons in developing countries are currently dependent on international relief assistance for their survival. Most of this assistance is provided by Western nations such as the United States. Mortality rates in these populations during the acute phase of displacement have been extremely high, up to 60 times the expected rates. Displaced populations in northern Ethiopia (1985) and southern Sudan (1988) have suffered the highest crude mortality rates. Although mortality rates have risen in all age groups, excess mortality has been the greatest in 1- through 14-year-old children. The major causes of death have been measles, diarrheal diseases, acute respiratory tract infections, and malaria. Case-fatality ratios for these diseases have risen due to the prevalence of both protein-energy malnutrition and certain micronutrient deficiencies. Despite current technical knowledge and resources, several recent relief programs have failed to promptly implement essential public health programs such as provision of adequate food rations, clean water and sanitation, measles immunization, and control of communicable diseases. Basic structural changes in the way international agencies implement and coordinate assistance to displaced populations are urgently needed.