Argentina elections: Voters pick new president
Argentines have been voting to choose a new president to replace Cristina Fernandez de Kirchner, who is constitutionally barred from seeking a third term.
Ms Fernandez, who stands down after eight years in power, says she leaves Argentines a better country.
Her hand-picked successor, left-winger Daniel Scioli, led opinion polls.
He is facing a strong challenge from the centre-right mayor of Buenos Aires, Mauricio Macri.
Another candidate, Sergio Massa, a former ally of Ms Fernandez, is polling behind Mr Macri. There are three other names on the ballot paper.
The BBC's Wyre Davies in Buenos Aires
Voting was brisk across the Argentine capital on Sunday.
In this country of more than 40 million people voting is compulsory and, in addition to the much-talked-about presidential choices, Argentines are also electing members of Congress, governors and other local representatives - so much patience was needed as the queues grew throughout the morning.
The presidential race will be tight and we might have to wait for some time before the official result is known - even then no clear winner may emerge, meaning a possible run-off at the end of November.
Nonetheless, most Argentines seemed to be taking their civic duty very seriously - there are very big challenges ahead for whoever replaces Cristina Fernandez de Kirchner.
Matching her charisma and appeal will be difficult but she has also arguably deeply divided Argentines on the future of their country, so compromise might be the order of the day for the next leader.
Long queues formed outside polling stations from the early hours of Sunday.
"We are voting today in a completely normal country," said Ms Fernandez said after casting her vote in the Patagonian town of Rio Gallegos.
In previous decades, Argentines always went to the polls "in the middle of a serious crisis," she added.
Ms Fernandez said achieving stability and leaving Argentines "a normal country" was the promise made by her late husband, Neston Kirchner, when he took office in 2003.
He died in 2010, three years after handing over the presidency to his wife.
Sunday sees the first round of voting. To win outright a candidate needs 45% of the vote or a minimum of 40% as well as a 10-point lead over the nearest rival.
Otherwise, there will be a run-off on 22 November.
Hedge funds battle
Whoever wins the presidency faces significant economic challenges.
While the country gained strength after a financial crisis in 2002, its economy, the third-largest in Latin America, has slowed in recent years, with GDP growing by only 0.5% last year.
The government is also locked in a battle against American hedge funds who disagree with how it wants to restructure $100bn (£65bn) of debt on which it defaulted in 2001.
While the firms successfully sued Argentina for repayment, Ms Fernandez refused to pay.
Mr Scioli, the governor of Buenos Aires province, is a former world powerboating champion who lost his right arm in a race in 1989.
Last week, he pledged tax cuts for workers earning under a certain income, a move expected to affect half a million people.
He has also vowed to bring down Argentina's inflation to single digits in less than four years and promises to introduce policy changes to invigorate the economy.
Thirty-two million Argentines are eligible to vote.