Need Round-Trip Ticket?

Is it required for US citizens to have a round-trip ticket when entering the Dominican Rep. as tourists? Can you enter with just one-way air-fare? What if they had extended (5-10 year) visas?

Thanx! Paul

All foreign nationals, unless they have a residency visa, need to show proof of their return ticket prior to boarding the airline that will take them to the DR. Foreign nationals arriving to the DR without return tickets could be sent back on the next flight out of the airline that brought them to the DR, on the airline's expense and therefore airlines are being more careful in requesting the return portion of the ticket.