Mexicans constitute about one in four of the foreign-born population in the US and far outnumber other source countries. Mexico is the leading source of unauthorised immigration to the US.

The US is growing more dependent on Mexican labour, and the two economies are becoming more integrated. In 2001, according to the US Embassy in Mexico City, the US processed 2,650,912 non-immigrant visa applications in Mexico. This was an increase of nearly 18% over the numbers of applications processed in 2000, which represented a 37 percent increase over the numbers of applications processed in 1999.

Facing increased pressure from the US to police its border, Mexico has participated in multilateral efforts to reduce poverty and decrease emigration. It joined a regional initiative to influence the US immigration reform debate. Mexico is beginning to see itself as a country of emigration, immigration, and transmigration, requiring a coherent migration policy, rather than one which simply reacts to US pressure.