International Attendee Travel

The ASTRO Annual Meeting is the world's premier gathering for the radiation oncology community. We welcome our international attendees and are providing these resources to assist you with your travel plans to the United States. We look forward to seeing you in Washington, DC, at ASTRO’s 2024 Annual Meeting.

Visa Process

The visa application process may require long lead times due to unprecedented demand in some countries, so we encourage attendees who are not U.S. citizens to apply for a visa as soon as they decide to travel to the United States, but ideally a minimum of 3-6 months in advance of their first day of travel. As many U.S. embassies and consulates have long visa interview wait times, we recommend that you review visa appointment wait times for the location where you will apply and take this into consideration when planning for your travel.

For additional information on what to expect if applying for a visa to the United States and to review visa application guidelines, please visit the U.S. Department of State’s website.

Visa Waiver Program

The U.S. Visa Waiver Program permits citizens of certain countries to travel to the United States for business or tourism for stays up to 90 days without obtaining a visa. Visa Waiver Program travelers are required to apply for and obtain approval authorization via the Electronic System for Travel Authorization (ESTA) prior to traveling to the United States. To learn more about how to apply for ESTA authorization, visit the U.S. Customs and Border Protection website.

Visa Application Tips

  • Include a letter of invitation from ASTRO.
  • When possible, provide proof of professional scientific and/or educational status, society membership and/or meeting registration.
  • Visa applicants are expected to provide evidence that they intend to return to their country of residence. Therefore, applicants should provide proof of binding or sufficient ties to their home country or permanent residence abroad.
  • All applicants must be able to qualify for a visa on their own merits under the requirements of the Immigration and Nationality Act.
  • Consider another embassy or consulate with shorter wait times, if feasible.

Letter of Invitation

ASTRO will provide a letter of invitation stating that you are registered to attend the ASTRO Annual Meeting once you are registered and paid in full, which may assist you in obtaining your travel visa. Registration opens in mid-May 2024. Visa letters are not available to attendees who are not paid in full, have registered to participate virtually or have canceled their registration.

If you are unable to receive a visa to leave your country or are unable to enter the United States, please contact the ASTRO Registration Center about changing your registration to Virtual Full Conference. In the event you are unable to travel, please be sure to review and cancel any other reservations or purchases you made regarding on-site activities, hotel accommodations and/or travel.

Questions about the Visa Process?

If you have any questions about the visa process, please contact your local embassy or consulate.


While ASTRO believes this information is correct, it is being provided only as a free convenience to assist our international attendees. In no event will ASTRO accept any responsibility for the accuracy or efficacy of this information and no information provided constitutes legal advice. International attendees are encouraged to check the relevant U.S. government sources for the latest information and to conduct their own research into visa requirements. If you have any specific questions regarding the type of visa you should be seeking, visa application process and/or have specific concerns, we advise you to contact a U.S. immigration law attorney and seek specific legal advice.

ASTRO cannot intervene on behalf of attendees with any U.S. embassies or consulates. Attendees are responsible for securing exit from their home country and entry into the United States.

American Society for Radiation Oncology
251 18th Street South, 8th Floor
Arlington, VA 22202
Telephone: 703-502-1550


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