American Democrats living in Italy were able to vote in the 'Super Tuesday' primaries thanks to polling stations set up in four Italian cities.
This was the first time that Americans in Italy and Italians with dual nationalities could take part in a US presidential primary.
The polling stations were set up by the organization Democrats Abroad in Milan, Florence, Rome and Bologna.
The polls remain open from 4pm to 9pm.
Among those with dual Italian-American citizenship who are voting is Italy's minister for sports and youth policy, Giovanna Melandri, who was born in New York when her father worked there for Italian state broadcaster RAI.
''I'm also an American citizen and today, for the first time in my life, I will vote in a primary election. It's a tough decision because they are two great candidates,'' Melandri said.
''In the end, I've decided to vote for (Barak) Obama because for the past 18 years two families have been living at the White House and I believe the time has come for a change,'' Melandri explained.
''However, this was not an easy decision because I was very tempted to vote for Hillary (Clinton),'' she added.
The US Democratic primary has sparked keen interest in Italy's new Democratic Party, which was recently created through the merger of the Democratic Left and centrist Daisy parties.
Italian Democrats are of two minds about Obama and Clinton, with party leader Walter Veltroni, the mayor of Rome, in favor of the black senator from Illinois, while ex-premier and former Democratic Left secretary Massimo D'Alema is reported to favor the New York senator and wife of ex-president Bill Clinton.
