The Visa Waiver Program (VWP) enables nationals of 37 participating countries to travel to the United States for tourism or business (visitor [B] visa purposes only) for stays of 90 days or less without obtaining a visa. Nationals of VWP countries* must meet eligibility requirements to travel without a visa on VWP, and therefore, some travelers from VWP countries are not eligible to use the program. VWP travelers are required to have a valid authorization through the Electronic System for Travel Authorization (ESTA) prior to travel, are screened at the port of entry into the United States, and are enrolled in the Department of Homeland Security’s US-VISIT program.