In most cases, foreign nationals who have been lawful permanent residents (green card holders) for five years can apply for naturalization and become a U.S. citizen. For lawful permanent resident spouses of U.S. citizens, the time period is three years. Congress has made it easier for military veterans to become naturalized U.S. citizens, as well as persons currently serving in the U.S. Armed Forces. Special rules and procedures apply to these members of the U.S. military.

For most naturalization applicants, there are specific requirements that apply concerning length of continuous residency in the United States. There are also requirements related to the ability to speak, read and understand English, and naturalization applicants must pass a test on United States history and government (civics). There are exceptions to the language and history/civics requirements based on age and disability.

To be eligible for naturalization, a foreign national has to be a person of "good moral character." Committing certain crimes will make someone ineligible for naturalization for lack of good moral character. Not telling the truth about past criminal offenses (even if they were committed as a juvenile and even if the criminal record was expunged!) will be considered lacking in good moral character. Police and criminal records are not the only things that will be considered in evaluating the foreign national's good moral character. The individual's general conduct will be examined, including, among other things, whether the individual has paid child support and alimony (if applicable), has paid taxes, registered for selective service, and what kind of driving record the individual has.

IMPORTANT: Please note that if a foreign national has committed certain serious crimes, that person should not apply to naturalize. In some cases, applying for naturalization may trigger the U.S. government to look into an old criminal conviction that would make the individual subject to removal (deportation). Anyone with a criminal record of any kind should consult with a competent immigration attorney before beginning the naturalization process.