In January 2004, President George Bush proposed the creation of a temporary worker program to allow more migrant workers to enter the US legally. This new temporary worker program would be open to undocumented workers in the US, as well as to prospective migrants currently residing abroad. The program would temporarily allow immigrants to fill jobs that, according to employers, would otherwise go unfilled at the current wage. The US Congress vetoed the presidential proposal, however, and requested a stricter enforcement of immigration law and the consequent deportation of undocumented immigrants. This study analyzes the economic effects of these immigration reforms on the US economy using an applied global general equilibrium model of migration. In this paper the global trade and migration model (GMig2) developed by Walmsley, Winters and Ahmed (2007) is modified to include a third labor category – undocumented unskilled – to reflect estimates of undocumented workers residing in the United States. The model is then used to analyze the impacts of two policy scenarios on the US economy: first, the deportation of undocumented workers currently residing in the US; and second, the legalization of undocumented agricultural workers. The first scenario is implemented through a decline in the number of undocumented workers residing in the US to zero, and a corresponding increase in the number of workers in Mexico. The second scenario is achieved by allowing undocumented workers to obtain legal status, thereby increasing their wages and productivity. We find that the deportation of undocumented workers causes a considerable loss to the US economy in terms of real GDP. Legalization of Mexican undocumented immigrants, on the other hand, is found to increase US real GDP. Hence the paper demonstrates there are clear advantages to the US economy of implementing proposals that both allow migrant workers to remain in the United States and increase the workers ability to participate freely in the US labor force as legal residents.