Canadian and Bermudian citizens can visit the USA for up to six months without a visa, while those from 35 other countries can visit for up to 90 days without a visa. Visitors should have a look at The Bureau of Consular Affairs website (http://travel.state.gov/visa/temp/without/without_1990.html) to determine whether or not they need a visa to enter Washington, DC and the USA.
Health and Safety
Although Washington, DC is known to have one of the highest murder rates in the country, the popular tourist areas are free from this. The poverty stricken areas of Anacostia and Northeast are the most unsafe areas in the city, especially at night. Some areas of Shaw and Adams Morgan can also become unsafe at night, though it is muggings that occur the most rather than violent crimes. The downtown area is the safest part of the city, though like in all big cities common sense should be used.
There are no major health concerns here, though traffic accidents are common. Be sure to travel with health insurance or the medical system can eat away at your savings. Hospitals here are excellent so on the off chance that a visitor falls ill they are sure to be in good hands.