In the past two decades, a tide of Mexican immigrants has settled illegally in the United States, and undocumented Mexicans today constitute an important component of the U.S. population. Yet due to their illegal status, information about the actual numbers of undocumented Mexicans, their living conditions, and the impact of their illegal status on their lives has been difficult to gather. In this book, the author analyzes the results of a unique survey conducted in Los Angeles County, where an estimated forty-four percent of the undocumented Mexican population lives. This survey allows the author to make explicit comparisons among groups of illegal and legal Mexican immigrants and to analyze the effects of their legal status on their living conditions.