Site: nolo.com
... It also might be valid for one or multiple entries. ... You will need to provide an updated letter from the organization, similar to the one you used to apply ... recommended to enter the U.S. for 90 days, travel to your home country, and immediately try to return for another ... Therefore, even if you're from one of the Visa Waiver countries, if your volunteer assignment will last ... Or, if you're spending fewer than 90 days in the U.S. and are from a Visa Waiver country, just make sure ... Getting a U.S. Visa (B-1) to Do Volunteer Work ...