The Immigration and Nationality Act allows for the immigration of foreigners to the United States based on relationship to a U.S. citizen or legal permanent resident.

IMMEDIATE RELATIVES

The following immediate relatives of U.S. citizens are eligible to qualify for immigration in the immediate relative category:
Spouse of a U.S. citizen; parent or step-parent of a U.S. citizen; child or stepchild under the age of 21 of a U.S. citizen. A separate petition must be filed for each person immigrating. Note: A step-parent or child will qualify for immigration only if the marriage creating the step parent/child relationship occurred before the child's eighteenth birthday.

How do I apply?
The first step in applying for an immigrant visa is for the U.S. citizen (petitioner) to file an immigrant visa petition, form I-130, with the U.S. Citizenship and Immigration Services (USCIS) in the U.S. The petitioner must submit his/her I-130 at the Service Center with jurisdiction over the petitioner's place of residence. USCIS maintains an office locator on its website: www.uscis.gov
Grandparents, aunts, uncles, in-laws and cousins cannot sponsor a relative for immigration.

Family First Preference (F1):Unmarried sons and daughters over the age of 21 of U.S. citizens and their minor children.
Family Second Preference (F2): Spouses, minor children and unmarried sons and daughters of lawful permanent residents.
Family Third Preference (F3): Married sons and daughters of U.S. citizens and their spouses and minor children.
Family Fourth Preference (F4): Brothers and sisters of United States citizens and their spouses and minor children provided the U.S. citizen is at least 21 years of age.

Filing the Immigrant Visa Petition
The US citizen or permanent resident relative of intending immigrants, who plan to base their immigrant visa application on family relationship, must submit a Petition for Alien Relative (Form I-130) to the Citizenship and Immigration Service office (CIS) in the United States Immigration through a family member. Once CIS approves the petition, they will forward the petition to the National Visa Center (NVC) that will contact the intending immigrant with further information.   (If the intending immigrant is in the United States and applying for Adjustment of Status, the procedure will be different.) 

LIMITS ON NUMBERS OF IMMIGRANT VISAS
U.S. law limits the number of immigrant visas that are available every year. This means that even if the CIS approves an immigrant visa petition for you, you may not get an immigrant visa immediately. In some cases, several years could pass between the time your immigrant visa petition is approved and the time when your immigrant visa is issued. Immigrant visas are issued in the chronological order in which the petition was filed until the numerical limit for the category is reached.

WHAT IS A PRIORITY DATE?
The filing date of the petition becomes the applicant’s priority date. Immigrant visas cannot be issued until the applicant’s priority is reached. Check the Visa Bulletin for the latest priority dates. CIS will send the approved immigrant visa petition to the National Visa Center where it will remain until the priority date is available. The National Visa Center will contact you with the “Instruction package for Immigrant visa applicants”. 

Immigrant Visa Interview

• The immigrant visa unit will schedule the final visa interview with the beneficiary. The petitioner is not required to attend the immigrant visa interview.
• The immigrant visa unit will send you information regarding the medical exam. Applicants must schedule their medical exam, and pay the medical fee directly to the clinic.
• Please, follow the instructions in the “Appointment package”. Failure to do so could result in a delay in your case.
• The consular officer cannot decide whether or not to issue you an immigrant visa until you formally apply and are interviewed.

After the visa is approved and issued.

Once the beneficiary has received his/her immigrant visa, s/he must enter the United States within 6 months of visa issuance. The Immigrant visa is placed inside the bearer’s passport, adhered to one of the pages. At the port of entry, upon the CBP officer’s placement of an admission stamp on the Machine Readable Immigrant Visa (MRIV) the alien is admitted to the United States as a permanent resident. This constitutes a temporary I-551 valid for one year from the date of the endorsement on the admission stamp. This endorsed stamp is acceptable for travel and employment purposes. Should the immigrant wish to leave the U.S. and his/her stamp has expired and s/he has not yet received the Alien Registration Receipt Card, s/he should contact CIS in the U.S. before departure to ensure permission to return to the United States.

A permanent resident alien who intends to remain abroad for an extended period of time should, at least 30 days prior to the proposed date of departure, apply while in the United States to the U.S. Citizenship and Immigration Services (USCIS) in the Department of Homeland Security for a Reentry Permit.   If the alien intends to remain outside the United States for over a year, the reentry permit is absolutely crucial.  However, it is also advisable for departures beyond 180 days.  The permit is valid for two years and may not be extended. If such a permit is obtained the alien may use this card to reenter the United States within the period of validity. Every alien applying for readmission must satisfy the immigration authorities that he or she is eligible in all respects.