Valid passport required by all nationals referred to in the chart above; validity varies - for most countries the passport must be valid for at least six months from the date on which the holder enters the USA. If not, the holder will be admitted until the expiration date on the passport; check with the embassy (see Contact Addresses).

(a) For nationals included in the Visa Waiver Program (see Visas), passports must be valid for at least 90 days from date of entry.
(b) All travellers entering the USA under the Visa Waiver Program require individual machine-readable passports. Children included on a parent's passport also now require their own machine-readable passport. Travellers not in possession of machine-readable passports will require a valid USA entry visa.
(c) As of 12 January 2009, all travellers visiting the US under the Visa Waiver Programme are to provide details online 72 hours prior to travel. For more information, please see below.
(d) Passports issued on or after 26 October 2005 will need to have a biometric identifier in order for the holder to travel visa free under the Visa Waiver Program (VWP). Machine-readable passports issued between 26 October 2005 and 25 October 2006 require a digital photograph printed on the data page or an integrated chip with information from the data page. Machine-readable passports issued on or after 26 October 2006 will require an integrated chip with information from the data page (e-passport).

Western Hemisphere Travel Initiative (WHTI): All persons, including US citizens, travelling by air between the USA and Canada, Central and South America, the Caribbean and Bermuda are required to present a valid passport, or other approved document, when entering or re-entering the USA. Similar requirements for those travelling by land or sea were introduced on 1 June 2009.

For further details about the Western Hemisphere Travel Initiative, visit the website of the US Department of State: (website: http://travel.state.gov/travel/cbpmc/cbpmc_2223.html).

Not required by nationals referred to in the chart above for stays of up to 90 days except: 
1. nationals of Bulgaria, Cyprus, Greece, Poland and Romania, who do require a visa as they are not included in the Visa Waiver Program.
2. holders of some Maltese passports are included in the Visa Waiver Program

(a) Landed Immigrants of Canada and British residents of Bermuda who are citizens of, and have valid passports from, Commonwealth countries or Ireland are not eligible to enter the USA without a visa.
(b) All passengers using US airports for transit purposes are required to obtain a transit visa. This does not affect qualified travellers travelling visa free under the Visa Waiver Program.
(c) To qualify for visa-free travel under the Visa Waiver Program, nationals must travel on a valid passport, for holiday, transit or business purposes only and for a stay not exceeding 90 days.  (ESTA). See below for more information.
(d) 2. Holders of UK passports with the endorsement British Subject, British Dependent Territories Citizen, British Protected Person, British Overseas Citizen or British National (Overseas) Citizen do not qualify for the Visa Waiver Program. A passport which states holder has right of abode or indefinite leave to remain in the UK does not qualify for visa free travel.
(e) A visa does not expire with the expiry of the holder’s passport. An unexpired, endorsed visa in an expired passport may be presented for entry into the USA, as long as the visa itself has not been cancelled, is undamaged, is less than 10 years old and is presented with a valid non-expired passport, provided that both passports are for the same nationality.
(f) Nationals of countries not referred to in the chart above are advised to contact the embassy to check visa requirements (see Contact Addresses).

ESTA: The Electronic System for Travel Authorization (ESTA) came into force on 12 January 2009. It is a fully automated, electronic system for screening passengers before they begin travel to the United States under the Visa Waiver Program. ESTA applications must be submitted at least 72 hours before travel to the USA. Some websites may charge you for the service but you can apply online for free at https. The granting of an ESTA does not guarantee entry to the USA.
://esta.cbp.dhs.gov/

Tourist, Business, Transit and Student: US$131.

Visas may be used for travel to the USA until the date it expires. Some visas are valid for multiple entries. The length of stay in the USA is determined by US immigration officials at the time of entry.

Embassy or consulate (see Contact Addresses).

Usually five after interview. Some cases may take up to 90 days – check with embassy/consulate (see Contact Addresses).