Four major principles underlie current U.S. policy on permanent immigration: the reunification of families, the admission of immigrants with needed skills, the protection of refugees, and the diversity of admissions by country of origin. Additionally, U.S. law provides for the temporary admission of various categories of foreign nationals, who are known as non-immigrants. They include a wide range of visitors, including tourists, foreign students, diplomats, and temporary workers. This book explores the immigration policy of the United States with regard to permanent and temporary admissions, with a focus on current law and policy, per-country ceilings, immigration patterns, and non-immigrant categories.