There are three ways to acquire U.S. citizenship: birth within the jurisdiction of the U.S.; birth abroad to citizen parents; and naturalization through legal process in the U.S.

General requirements:

The general requirements for naturalization according to the Immigration Act of 1990 are as the following:

• Admitted to the U.S. as a Lawful Permanent Resident;
• Must be eighteen years of age;
• Upon filing of the application, must be continuous residence in the U.S. for at least five years;
• Physical presence in the U.S. for at least fifty percent of the time during the statutory period (i.e. thirty months);
• Good moral character during the statutory period
• Possess the ability to read, write, speak, and understand the English language unless exempt from this requirement;
• Willingness to take the oath of allegiance to the U.S. without mental reservation; and have an intention to reside permanently in the U.S.

Special Requirements for Naturalization

There are "special requirements" for naturalization of certain classes of persons, such as members of the armed forces, U.S. government employees, as well as the spouses of U.S. citizens.

-Member of armed force: U.S. Citizenship and Immigration Services (USCIS) streamlines the application and naturalization process for current members of the military and those who were recently discharged. A member of the U.S. armed forces must meet the requirements and qualifications to become a citizen of the United States that include the following:

• Good moral character;
• Knowledge of the English language;
• Knowledge of U.S. government and history (civics); and
• Attachment to the United States by taking an Oath of Allegiance to the U.S. Constitution.

-Spouses of U.S. Citizens Employed Abroad: For the spouse of a citizen where the U.S. citizen spouse is temporarily employed abroad with a qualifying organization. The citizen spouse must be:

• An employee of the U.S. government, an American institution of research, a public international organization of which the U.S. is a member, or an American company: or he/she must be engaged as a missionary or religious worker.
• The applicant must have been admitted to the U.S. as a Lawful Permanent Resident;

-A spouse of a U.S. citizen is eligible for naturalization if he/she meets all the above requirements except that, the required length of continuous residence is shortened to three years, and the minimum physical presence requirement consequently becomes eighteen months rather than thirty.