When this volume was published in 1990, undocumented Mexican immigrants had become an important component of the US population. In this book the author analyzes the results of a unique survey conducted in Los Angeles County, where an estimated 44 percent of the undocumented Mexican population lived. The survey allows the author to make comparisons among the groups of undocumented and legal Mexican immigrants and to study the effects of legal status on their living conditions. The author also examines the findings of a number of other social scientists, providing a comprehensive summary of the data on undocumented Mexicans in the US. In his conclusion, he turns to an evaluation of policy options for incorporating this group into the US population and for immigrants. The book will be useful to sociologists and other social scientists as well as to lawyers and policy experts studying the problem of illegal immigrants.