A passport that is valid for at least three months beyond the end of your trip is required to enter Italy. No visa is required for U.S. citizens staying 90 days or less, but Italian law requires you to declare yourself upon entering the country. If you are staying less than 90 days, you must have your passport stamped by immigration on the day of your arrival.
If you plan to stay more than three months, you must obtain a visa from the Italian Embassy or a Consulate before you arrive and a permit of stay (permesso di soggiorno) once your enter the country. For assistance with a visa, visit the Italian Embassy website at http://www.ambwashingtondc.esteri.it/ambasciata_washington. You can pick up an application for the permesso di soggiorno at any national post office in Italy.
No immunizations are required for U.S. citizens traveling to Italy, but the Centers for Disease Control (CDC) recommends you have all of your routine vaccines up to date. These include chicken pox, polio, measles, mumps, rubella, diphtheria and tetanus.
Nobody wants to think about emergencies during a vacation, but they happen. Before you go, register your trip with the U.S. Department of State at https://travelregistration.state.gov/ibrs/ui/ so that your contact information is on file. In you need emergency help in Italy, dial 113, the Italian equivalent of 911.
Keep track of what you buy. Each U.S. citizen is allowed a duty-free personal exemption of $800 for the items bought in Italy and brought back to the U.S. You have to pay duty on purchases exceeding this limit. One way to buy more is to travel with your family. Family members who live in the same house can combine their personal exemptions. So for a family of four traveling together, the total exemption is $3,200.