The U.S. Department of Homeland Security (DHS) recently added Greece to the list of countries authorized to participate in the Visa Waiver Program (VWP). Under the Visa Waiver Program, citizens and eligible nationals of participating countries may apply for admission to the United States at U.S. ports of entry as visitors for business or pleasure for a period of ninety days or less without first obtaining a nonimmigrant visa, provided that they are otherwise eligible for admission. Such travelers, however, must obtain an approved travel authorization at least 72 hours in advance of travel via the Electronic System for Travel Authorization (ESTA). The ESTA web-based system is administered by DHS at https://esta.cbp.dhs.gov free of charge. ESTA authorization does not guarantee admission by a Customs and Border Protection official at a U.S. port of entry, and ESTA is not available to foreign nationals who have been previously refused a visa.