The Pew Hispanic Center conducted an unprecedented survey of Mexican migrants in the United States, including thousands who say they have no U.S.-issued identity documents. Provides detailed information on the demographic characteristics, living arrangements, work experiences and attitudes toward immigration of 4,836 Mexican adults who completed a 12-page questionnaire as they were applying for a matricula consular, an identity document issued by Mexican diplomatic missions. Fieldwork was conducted in Los Angeles, New York, Chicago, Atlanta, Dallas, Raleigh, NC, and Fresno, CA, from July 12, 2004, to Jan. 28, 2005.