Citizens of all countries except Canada are required to have the appropriate visa in their passports if they are to enter the U.S. in a specific nonimmigrant classification - be it to study, to work or conduct research, or even to be a tourist. Visa waivers: In certain limited circumstances, citizens of some countries are exempt from being required to have a visa when coming to the U.S. as a visitor for business or for pleasure for periods of 90 days or less.
Visas can only be obtained at a U.S. consulate outside the United States. If you have a valid visa in your passport for the immigration status you are seeking, you generally will not need to obtain a new one. If the visa is expired or if you changed your immigration status inside the U.S., you will need to apply for a new visa, in order to re-enter the U.S. in the desired immigration status.
Application procedures vary considerably from one country to another. Scholars should research the requirements. If you have a visa interview, it will be short. During the interview, you must make a good impression. Be positive and respond to the questions with clear, concise answers. If your spouse and children will remain in your country, be prepared to explain how they will support themselves in your absence.
Learn about the J-1 Visa Exchange Visitor Program for Professors and Scholars.