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. 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). Children 15 and under may continue entering with only a U.S. birth certificate, or other proof of U.S. citizenship. Note: These rules are in effect for U.S. citizens who wish to visit Tijuana for the day, as well.
It is advised to always have at least one or two consecutive blank pages in your passport to allow space for visas and stamps that need to appear together. It is also important to note when your passport expires. In general, your passport should have at least 6 months left before its expiration; the U.S. does have an agreement with many countries (including Australia, Canada, Ireland, New Zealand, and the U.K.) that allows for use of a current passport up to the actual date of expiration. If you are traveling without a visa, though, you will only be admitted until the date of your passport's expiration. For other information, contact the following passport offices:
For Residents of Australia -- Contact the Australian Passport Information Service at tel. 131-232, or visit www.passports.gov.au.
For Residents of Canada -- Contact the central Passport Office, Department of Foreign Affairs and International Trade, Ottawa, ON K1A 0G3 (tel. 800/567-6868; www.ppt.gc.ca).
For Residents of Ireland -- Contact the Passport Office, Setanta Centre, Molesworth Street, Dublin 2 (tel. 01/671-1633; www.foreignaffairs.gov.ie).
For Residents of New Zealand -- Contact the 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).
For Residents of the 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).
For Residents of the United States -- To find your regional passport office, check the U.S. State Department website (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 a US$14 fee for the online application. 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 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).
Every visitor 21 years of age or older may bring in, free of duty, the following: (1) 1 U.S. quart of alcohol; (2) 200 cigarettes, 50 cigars (but not from Cuba), or 3 pounds of smoking tobacco; and (3) $100 worth of gifts. These exemptions are offered to travelers who spend at least 72 hours in the United States and who have not claimed them within the preceding 6 months. It is forbidden to bring into the country almost any meat products (including canned, fresh, and dried meat products such as bouillon, soup mixes, and so on). Generally, condiments including vinegars, oils, pickled goods, spices, coffee, tea, and some cheeses and baked goods are permitted. Avoid rice products, as rice can often harbor insects. Bringing fruits and vegetables is prohibited since they may harbor pests or disease. International visitors may carry in or out up to $10,000 in U.S. or foreign currency with no formalities; larger sums must be declared to U.S. Customs on entering or leaving, which includes filing form CM 4790. For details regarding U.S. Customs and Border Protection, consult your nearest U.S. embassy or consulate, or U.S. Customs (www.customs.gov).
For information on what you're allowed to take home, contact one of the following agencies:
Canadian Citizens: Canada Border Services Agency, Ottawa, Ontario, K1A 0L8 (tel. 800/461-9999 in Canada, or 204/983-3500; www.cbsa-asfc.gc.ca).
U.K. Citizens: HM Customs & Excise, Crownhill Court, Tailyour Road, Plymouth, PL6 5BZ (tel. 0845/010-9000; from outside the U.K., 020/8929-0152; www.hmce.gov.uk).
Australian Citizens: Australian Customs Service, Customs House, 5 Constitution Ave., Canberra City, ACT 2601 (tel. 1300/363-263; from outside Australia, 612/6275-6666; www.customs.gov.au).
New Zealand Citizens: New Zealand Customs, The Customhouse, 17-21 Whitmore St., Box 2218, Wellington, 6140 (tel. 04/473-6099 or 0800/428-786; www.customs.govt.nz).
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. If you have a medical condition that requires syringe-administered medications, carry a valid signed prescription from your physician; syringes in carry-on baggage will be inspected. Insulin in any form should have the proper pharmaceutical documentation. If you have a disease that requires treatment with narcotics, you should also carry documented proof with you -- smuggling narcotics aboard a plane carries severe penalties in the U.S.
For HIV-positive visitors, requirements for entering the United States are somewhat vague and change frequently. For up-to-the-minute information, contact AIDSinfo (tel. 800/448-0440 or 301/315-2816 outside the U.S., TTY 888/480-3739; www.aidsinfo.nih.gov) or the Gay Men's Health Crisis (tel. 800/243-7692 or 212/367-1000; www.gmhc.org).
Note: This information was accurate when it was published, but can change without notice. Please be sure to confirm all rates and details directly with the companies in question before planning your trip.