The number of foreign-born people residing in the United States is at the highest level in our history and, as a portion of the U.S. population, has reached a percentage not seen since the early 20th century. The actual number of unauthorised aliens in the United States is unknown. The three main components of the unauthorised resident alien population are aliens who overstay their non-immigrant visas; aliens who enter the country surreptitiously without inspection; and aliens who are admitted on the basis of fraudulent documents. In all three instances, the aliens are in violation of the Immigration and Nationality Act (INA) and subject to removal. This book will analyse components of the unauthorised population and discuss policy options to provide relief to selected subgroups of particular congressional and public interest.