More than 250 million people enter and exit the U.S. each year. Many cross the border repeatedly, some legally and some illegally. In the wake of the terrorist attacks of September 11, Americans have re-ignited a national discussion on immigration.

At the center of the debate is the role of the U.S. government's Immigration and Naturalization Service which is supposed to keep track of who enters and exits the country. Neal Lavon reports on the new immigration debate in this edition of Dateline.