Generally either a close family relative or an employer must sponsor someone to become a permanent resident in the U.S. The first method relies on a close tie to a U.S. citizen or permanent resident. If a foreign national does not have such a relative, he or she might qualify through a sponsor employer. There are five employment-based categories that a foreign national may fall under if applying to become a permanent resident.

Currently, the law sets an annual limit of 226,000 immigrant "preference" numbers for family-based categories, and at least 140,000 immigrant "preferences" numbers for employment-based categories.

For most employees, labor certification will be a prerequisite for obtaining employment-based permanent residence. The law requires that any foreign national who seeks to enter the U.S. to perform skilled or unskilled labor is not admissible unless the U.S. Secretary of Labor certifies that there are not sufficient U.S. workers available for the position, and that employment of the foreign national will not adversely affect the wages and working conditions of similarly employed U.S. workers.