For flights leaving Chile, there is an airport tax of USD$18, or the equivalent in CHP (Chilean pesos). On domestic flights airport tax is usually included in the airline ticket. US citizens pay a reciprocity tax of USD$100 in cash upon entry into the country.  The receipt is valid for the life of your passport. This tax is applied to countries that charge Chilean citizens a fee to process visas.

The Santiago International Airport Comodoro Arturo Merino Benítez, and the following airports: Arica (Chacalluta), Antofagasta (Cerro Moreno), Iquique (Cavancha), Puerto Montt (Tepual), Osorno, Concepción, Punta Arenas (Pdte. Ibañez) and Temuco (Manquehue) provide the following services: international police, immigration, customs and other basic facilities such as restaurants, bathrooms, gift shops, newspaper and magazine stands, and waiting areas.

Foreign travelers must pass through customs inspection when entering the country. If you are carrying only personal items you shouldn't have any problems, as long as you do not possess: 

• Fruits, seeds, vegetables or non-processed animal products.
• Firearms, ammunition or explosives.
• Illegal drugs