Brazil has reciprocal arrangements for visas with each country. It is therefore sometimes difficult to grasp exactly what the rules are for each particular circumstance that is not a straight forward tourist situation. Here we give an overview of Tourist, Work and Semi resident situations.
U.S. citizens need a valid visa and passport to enter Brazil. There are no airport issued visas for U.S. citizens and you need to have obtained your visa from the local embassy or consulate before traveling. The website for the Brazilian Embassy in Washington D.C. (along with consular information) can be found here: http://www.brasilemb.org
Following the introduction of photographing and finger printing of Brazilian Nationals at American immigration, American Citizens now undergo a identical procedure on arrival in Brazil.
If you are traveling on a recognised first world passport you are entitled to stay for up to six months, granted in two allotments of 90 days. When you arrive in Brazil immigration will ask you how many days you are staying for and you can reply with any number up to 90 days. This number will be written on your tourist card (keep this safe). If you are staying for more than 90 days you will still have to say 90 and then before those 90 days elapses you will need to apply for a visa extension with the Federal Police for the remainder of your trip. Under normal circumstances the extension is just a formality. For some strange reason you are not allowed to enter Federal Police buildings wearing shorts.
You are required to carry identification with you at all times in Brazil. A plastification or photocopy of your passport is suitable for tourists.
Work visas can only be granted once you have an offer of employment from the organisation you are going to work for. This doesn't count if you are working for an NGO. In that case you will be employed as an unpaid volunteer and you will have to sign a disclaimer with the NGO and enter and exit Brazil as a tourist. Foreigners are allowed to work in Brazil, see Jobs and Employment for more details.
Overstaying 180 days.
Once the 180 days has elapsed you have to leave Brazil - or pay a fine for the number of days you stay over (currently R$8 per day). Whilst some nationalities can return after a weekend in Buenos Aires or Asuncion you are now legally obliged to pay tax (at 25% of you declared global income). Speak to a local accountant if you are in this situation.
Living in Brazil for part of the year.
If you are in the desirable position of been able to live in Brazil for part of the year and your home country for the remainder there are two other things you should really do. The first is apply for your C.P.F. (Cadastro Pessoa Fisica.) either through a lawyer or directly at Receita Federal, the former is generally easier. This is an identification card and gives you legal entity in Brazil (which you will need to buy things like real estate.) You will also be asked for your C.P.F. in various situations from joining a gym to buying a coffee table from Tok Stok (a furniture store). The second is to apply for a C.N.E. Cartão Nacional Estrangeiro which is issued by the Federal Police. The primary reason for getting the C.N.E. is to enable yourself to open a local bank account. You can only get the C.N.E after the C.P.F. Neither of these cards are residency per se but they are legal identity cards and are valid if you are asked to prove who you are. (Remember you are legally obliged to carry identification at all times in Brazil.) Ownership of a C.P.F. and C.N.E. will make things less bureaucratic for you when you want to do something in Brazil.