Anthropologists tell us that human beings have been migrating since Homo erectus left Africa for Eurasia a million years ago. After occupying Africa 150,000 years ago, Homo sapiens migrated out of Africa about 70,000 years ago and began arriving in the Americas about 20,000 years ago. Even though the reasons for these historically very remote migrations are unclear, what is clear though is that migration forms an important part of human history and continues to do so. Modern humans migrate voluntarily, are forced to migrate through hostile circumstances, or they are enslaved and transported against their will. Voluntary migration generally occurs because people seek better economic, social, or political opportunities. Forced migration occurs because people flee war, persecution, or famine. Enslavement has occurred throughout history, but the forced transport of 20 million native Africans to North America from the 1600s to the 1800s represents one of the most shameful coerced migrations in human history. Migration of people from Europe to the United States has been a major source of population growth and cultural change even before the time of the American Revolution. In the Great Atlantic Migration (1830-1910), some 37 million people migrated from Europe to a welcoming United States. And others from Asia came to work in the United States to build the trans-continental railroad. These 19th and early 20th century migrants sought a better life and greatly enriched the racial, ethnic, and cultural diversity of America and created the American ''melting pot'' of today. Contemporary migration to the United States chiefly occurs now from China, India, the Philippines, and, especially, from Mexico and Central America. Attitudes about Mexican worker migration to the United States have often been politically in conflict. The demand for manual labor during World War II led the United States to enter into a series of diplomatic agreements with Mexico to allow entry of temporary contract laborers from Mexico into the United States (called the Bracero Program). After the expiration of the initial agreements in 1947, the program was continued, but limited to the agricultural sector, until its official expiration in 1964. Mexican migration, however, did not cease in 1964. Since then, millions of Mexican nationals have migrated to the United States seeking employment opportunities chiefly in the agriculture, construction, and service sectors, many without ''authorization'' to enter the United States. Yet, after 1975, when Congress passed legislation to permit the resettlement of Southeast Asian refugees in the aftermath of the Vietnam War, and after 1986, when the Immigration Reform and Control Act granted amnesty to about 3 million unauthorized migrants, American attitudes about Mexican migration became increasingly hostile. Starting in the mid-1990s, public debate has centered around toughening border enforcement, building fences along the international border with Mexico, expanding grounds for deporting Mexican nationals, enhancing restrictions on the hiring of unauthorized migrants, closing opportunities for unauthorized migrants to legalize their status, and limiting their access to social safety-net services. Seldom heard in the recent public policy debates about migration of workers into the United States has been any recognition of the value that migrant workers add to the American economy or the price they pay in work-related injury and illness. Migrants enter the United States to better their lives through work and their labor helps sustain the global competitiveness of the American economy. However, that contribution is not without cost to them and to their families. An increasing literature indicates that migrant workers in the United States, and in other countries around the world, bear a disparate burden of occupational fatalities, injuries, and illnesses as compared to the non-migrant or native workforce. It is timely, then, that this edition of the American Journal of Industrial Medicine focuses our attention on the contemporary global migration of workers and the burden of occupational injuries and illnesses they bear. The article, ''A Global Perspective of Migration and Occupational Health'' by Marc Schenker, and additional articles on the migrant workforces of the United States, Spain, and South Africa, make clear that we need to turn our collective attention to the occupational health issues of migrant workers. The papers in this edition of the Journal make the case for why we need to increase our awareness of the plight of migrants within our own workplaces; why we need to develop special methods to address the challenges associated with doing research with mobile migrant workers; the importance of conducting research on day laborers, garment workers, and workers who toil in the American ''underground'' economy; and why it is important to formulate actions to address migrant occupational health issues. We need to meet these challenges for a number of reasons. Not the least of these reasons is the fact that of all the countries who ''host'' large migrant workforces, the United States has largest migrant workforce by far (United Nations, 2002). The National Institute for Occupational Safety and Health (NIOSH) supports efforts to expand our current efforts to conduct migrant occupational health research- research that is so well-represented by the authors' papers in this edition of the Journal. But, as Marc Schenker points out in his paper, the research road is not without its obstacles-there are many barriers to studying migrants' occupational health issues. Among those barriers are the ''large proportion of informal work arrangements, use of labor intermediates, short-term job placements, and absence of standard identification data (e.g., Social Security number).'' Foremost among the tasks we need to tackle to produce a robust fund of knowledge about migrants' occupational health ''is the need to develop new epidemiologic tools and methods.'' Such work needs to start now and NIOSH stands ready to help promote the development of those much-needed research methods. NIOSH has already established an occupational health disparities research program which can be a home for developing methods specifically suited to migrant occupational health research (see http://www.cdc.gov/niosh/programs/ohd/
). I applaud all the authors of this edition of the Journal for their work in bringing the occupational health issues of migrant workers better focus for us all. Thank you for your work.