As the world becomes increasingly interdependent and the health of people and the health of national economies are similarly inter-related, growing numbers of public and private institutions are recognizing the importance of "global health research." Not only do people cross borders — as migrants, immigrants, or transnationals moving back and forth between countries — but so do health problems and their underlying determinants, gradually eroding national differences in health burdens, threats, and responses to them. Global public health research focuses on the inter-relationships among local, regional, national, and international factors that influence health and on the development of effective interventions and policies that will address these factors.