The proposed research will evaluate the impact of undocumented Mexican workers on the wages and employment of low-skilled U.S. workers residing in the southwestern U.S. The study will compare changes between 1970 and 1975 in the structure of wages and employment in this labor market which is believed to be directly affected by illegal Mexican immigration. Other regions of the U.S. will be used to control for other influences on wages and employment that cannot be measured explicitly. The data sets employed will be the 1970 Census and the 1975 Survey of Income and Education. The U.S. will be divided into two regions - one which is believed to be heavily impacted by illegal immigrants, and another which is believed to be relatively free of this group. By comparing the earnings and employment equations estimated for the Southwest region to the earnings and employment equations estimated for the control region in both 1970 and 1975, it will be possible to measure the extent to which low-skill workers in the Southwest were adversely impacted by events that occurred between these years. When influences such as internal migration, a changing industrial structure, and changing levels of skill are removed, the net change in earnings and employment can be reasonably interpreted as the result of illegal immigration.