Virtually every air traveler entering the U.S. is required to show a passport. All persons, including U.S. citizens, traveling by air between the United States and Canada, Mexico, Central and South America, the Caribbean, and Bermuda are required to present a valid passport. Note: U.S. and Canadian citizens entering the U. S. at land and sea ports of entry from within the Western Hemisphere must now also present a passport or other documents compliant with the Western Hemisphere Travel Initiative (WHTI; visit www.getyouhome.gov for details). Children 15 and under may continue entering with only a U.S. birth certificate, or other proof of U.S. citizenship.
Australia -- Australian Passport Information Service (tel. 131-232, or visit www.passports.gov.au).
Canada -- Passport Office, Department of Foreign Affairs and International Trade, Ottawa, ON K1A 0G3 (tel. 800/567-6868; www.ppt.gc.ca).
Ireland -- Passport Office, Setanta Centre, Molesworth Street, Dublin 2 (tel. 01/671-1633; www.foreignaffairs.gov.ie).
New Zealand -- Passports Office, Department of Internal Affairs, 47 Boulcott St., Wellington, 6011 (tel. 0800/225-050 in New Zealand or 04/474-8100; www.passports.govt.nz).
United Kingdom -- Visit your nearest passport office, major post office, or travel agency or contact the Identity and Passport Service (IPS), 89 Eccleston Sq., London, SW1V 1PN (tel. 0300/222-0000; www.ips.gov.uk).
United States -- To find your regional passport office, check the U.S. State Department website (www.travel.state.gov/passport) or call the National Passport Information Center (tel. 877/487-2778) for automated information.
The U.S. State Department has a Visa Waiver Program (VWP) allowing citizens of the following countries to enter the United States without a visa for stays of up to 90 days: Andorra, Australia, Austria, Belgium, Brunei, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Japan, Latvia, Liechtenstein, Lithuania, Luxembourg, Malta, Monaco, the Netherlands, New Zealand, Norway, Portugal, San Marino, Singapore, Slovakia, Slovenia, South Korea, Spain, Sweden, Switzerland, and the United Kingdom. (Note: This list was accurate at press time; for the most up-to-date list of countries in the VWP, consult www.travel.state.gov/visa.) Even though a visa isn't necessary, in an effort to help U.S. officials check travelers against terror watch lists before they arrive at U.S. borders, visitors from VWP countries must register online through the Electronic System for Travel Authorization (ESTA) before boarding a plane or a boat to the U.S. Travelers must complete an electronic application providing basic personal and travel eligibility information. The Department of Homeland Security recommends filling out the form at least 3 days before traveling. Authorizations will be valid for up to 2 years or until the traveler's passport expires, whichever comes first. Currently, there is one US$14 fee for the online application. Existing ESTA registrations remain valid through their expiration dates. Note: Any passport issued on or after October 26, 2006, by a VWP country must be an e-Passport for VWP travelers to be eligible to enter the U.S. without a visa. Citizens of these nations also need to present a round-trip air or cruise ticket upon arrival. E-Passports contain computer chips capable of storing biometric information, such as the required digital photograph of the holder. If your passport doesn't have this feature, you can still travel without a visa if the valid passport was issued before October 26, 2005, and includes a machine-readable zone; or if the valid passport was issued between October 26, 2005, and October 25, 2006, and includes a digital photograph. For more information, go to www.travel.state.gov/visa. Canadian citizens may enter the United States without visas, but will need to show passports and proof of residence.
Citizens of all other countries must have (1) a valid passport that expires at least 6 months later than the scheduled end of their visit to the U.S.; and (2) a tourist visa.
For information about U.S. Visas go to www.travel.state.gov and click on "Visas." Or go to one of the following websites:
Australian citizens can obtain up-to-date visa information from the U.S. Embassy Canberra, Moonah Place, Yarralumla, ACT 2600 (tel. 02/6214-5600) or by checking the U.S. Diplomatic Mission's website at http://canberra.usembassy.gov/visas.html.
British subjects can obtain up-to-date visa information by calling the U.S. Embassy Visa Information Line (tel. 09042-450-100 from within the U.K. at £1.20 per minute; or tel. 866-382-3589 from within the U.S. at a flat rate of $16 and is payable by credit card only) or by visiting the "Visas to the U.S." section of the American Embassy London's website at http://london.usembassy.gov/visas.html.
Irish citizens can obtain up-to-date visa information through the U.S. Embassy Dublin, 42 Elgin Rd., Ballsbridge, Dublin 4 (tel. 1580-47-VISA  from within the Republic of Ireland at €2.40 per minute; http://dublin.usembassy.gov).
Citizens of New Zealand can obtain up-to-date visa information by contacting the U.S. Embassy New Zealand, 29 Fitzherbert Terrace, Thorndon, Wellington (tel. 644/462-6000; http://newzealand.usembassy.gov).
For customs information, consult your nearest U.S. embassy or consulate, or the U.S. Customs website at www.customs.gov. In Washington, D.C., the U.S. Customs and Border Protection agency has an office at 1300 Pennsylvania Ave. NW, Washington, DC 20229, www.cbp.gov; tel. 877/287-8667.
Unless you're arriving from an area known to be suffering from an epidemic (particularly cholera or yellow fever), inoculations or vaccinations are not required for entry into the United States.