There is nothing new about homelessness. There have been homeless people for some 10,000 years—from the time when humans built their first permanent homes in the first towns of the Fertile Crescent. The historical record, novels and poems, and sacred texts tell us the stories of beggars, wandering ascetics, penniless friars, displaced peasants, lost soldiers, street youths, vagrants, new arrivals in the city, and displaced workers. Homelessness has changed over the years. In the United States, during the late nineteenth century, it was hoboes and tramps who drew the attention of the public, the police, and then the social reformers of the Progressive Era. From the 1920s through the Great Depression, attention shifted to the skid rows, home to transient workers and retired single men. The decline of skid rows in the 1970s was followed by a new era of homelessness with many formerly institutionalized people—who had untreated or poorly treated emotional disorders—winding up on the streets of America. In the 1980s, the nature of homelessness changed again. Growing economic inequality, racism, a permanent decrease in the number of well-paid unskilled jobs, and a lack of affordable housing combined to make several million people—many of them African-American women and their children—homeless on America’s streets, in shelters, in motels, and in substandard and temporary apartments. This pattern continues in 2004. Homelessness is not just a U.S. problem, although when viewed cross-culturally, it becomes a more complex issue. In many developed nations, homeless families, many of them immigrants, are the major issue. In the developing nations of Asia, Africa, and Latin America, the homeless are often women and their children, youths, and migrants from rural areas who have come to cities looking for work and opportunity. The emergence of many cities in developing nations as major regional or global commercial centers has made the problem even worse, by increasing the appeal of cities as employment centers to the rural poor while at the same time providing less and less affordable housing and support services for immigrants. The goal of the Encyclopedia of Homelessness is to summarize our knowledge of homelessness. This includes describing the patterns of homelessness in the past, focusing on the recent and current situation in the United States, and sampling homelessness around the world. Entries cover causes; history; legal issues, advocacy, and policy; legislation and programs; lifestyle and health problems; organizations; research; services and service settings; size and perceptions; subpopulations and lifestyles; and world issues and perspectives. Descriptive articles cover homelessness today in eight major American cities and more than thirty cities and nations around the world. These entries allow for quick and easy comparisons.