The number of immigrant visas available annually is set under the United States Immigration and Nationality Act. If you're an immediate relative -- spouse, parent or unmarried child under age 21 -- of a U.S. citizen, the number of visas are unlimited so you can apply in any year. If you're hoping to immigrate based on a preference category, such as skilled labor, the number of annual visas is limited.
Visa Sponsorship and Petition
Potential U.S. immigrants require sponsorship, either from a relative with U.S. citizenship or permanent resident status, or a prospective employer. Your sponsor must file a petition for you with U.S. Citizenship and Immigration Services. Citizens and permanent residents file Form I-130, the "Petition for Alien Relative," while employers must file Form I-140, the "Petition for Alien Worker." Once USCIS approves the petition, the visa application process begins.
Required Documentation
Once your petition is approved, you can apply for a visa at your country's U.S. embassy or consulate. You must supply up-to-date documents for visa processing. You must fill out a biographical data questionnaire, answering all questions truthfully, and submit both an original and copy of both your sponsor's and your birth certificate. If either birth certificate is not in English or in the language of your country, a notarized translation is required. If married, you must submit the original and a copy of your marriage license. The original, signed Form I-864, "Affidavit of Support" from your sponsor is required. Additionally, you must provide any prior non-immigrant U.S. visas, along with a valid passport from your country.
Medical Examination
All immigrants must undergo a medical examination by a qualified doctor. The U.S. Department of State designates foreign physicians who can conduct these examinations. The U.S. embassy or consulate in your country can give you information regarding eligible "panel physicians." You must bring Form I-693, the "Report of Medical Examination and Vaccination Record" to your medical appointment. After the doctor conducts the examination, he fills out the form and signs and seals it. Only sealed envelopes are accepted by the USCIS.
Visa Interview
Once you have submitted all necessary documentation and received your medical examination, you can set up a visa interview appointment. You must bring your appointment letter issued by the embassy or consulate to the actual interview, along with all of your other documentation. The U.S. Department of State warns that you should not make nonrefundable flight plans or make "permanent financial commitments," such as quitting your job or selling your house until after the interview and after receiving your immigration visa.