If you're going on a business trip to Italy and plan on renting or driving a car, you'll want to make sure you obtain an International Drivers Permit (note: it's sometimes called an International Driving License).
In the U.S. they can be obtain at AAA offices as well as from the National Automobile Club, typically for a fee of $15.
Italian law requires drivers that don't have an EU driving license to show their home country license as well as an International Driving Permit if (or when) they're pulled over. Your rental car company may or may not require one or even ask about one. It's the traveler's responsibility to ensure he or she has the appropriate paperwork. Of course, if you're lucky and don't get stopped while driving in Italy, you won't need to use the International Driving Permit, but in either case, it's well worth the small fee to have peace of mind.
For additional information on navigating Italian roads, road signs, and more, the Slowtrav.com website has a good explanation of driving in Italy that's worth consulting.