Argentines have been voting for a new president to succeed Nestor Kirchner, with his wife Cristina Fernandez de Kirchner seen as the clear favourite.
Cristina Fernandez de Kirchner has consistently led the opinion polls
Opinion polls suggest Mrs Kirchner could win enough votes to avoid a second round run-off next month.
Her main rivals are a former beauty queen, Elisa Carrio, and Mr Kirchner's ex-Economy Minister Roberto Lavagna.
Mr Kirchner has governed for the past four years, but surprised the nation by deciding not to seek a fresh term.
Polling was extended by one hour in some parts of the country to 1900 local time (2200 GMT) to accommodate a late rush of voters.
Besides a new president, voters were choosing eight provincial governors, a third of the Senate and about half of the Chamber of Deputies.
Some 27 million people were eligible to vote and people attended polling stations under sunny skies across most of the country.
After casting her vote in her south Patagonian home town of Rio Gallegos, Mrs Kirchner kissed supporters and declared it was "an important day for the continuation of democracy".
"I'm part of the generation that grew up and couldn't vote for anything," she added, referring to the military dictatorship of 1976-83.
Economy and crime
To win in the first round, a candidate needs to win either 45% of the vote, or 40% if they are 10 percentage points ahead of their nearest rival.
Recent opinion polls suggested Mrs Kirchner could win between 39.5% and 49.4% of votes.
If she wins, she will be the first woman elected president of Argentina.
The economy and rising crime have been the two main issues in campaigning.
President Kirchner has overseen a return to stability and some prosperity since the economy collapsed six years ago, plunging thousands into poverty, the BBC's Daniel Schweimler reports from Buenos Aires.
But there are fears over how strong the economy really is and general scepticism over official statistics suggesting inflation is under control.
Ms Carrio, the candidate of the centre-left Civic Coalition, is running on an anti-corruption platform and is promising to reduce economic inequality.
She has urged the poorest to vote for her in order to take the election to a second round on 25 November.
Roberto Lavagna and Elisa Carrio are Mrs Kirchner's main rivals
The other 12 candidates include Mr Lavagna of the centrist Coalition for an Advanced Nation and a well-known free-market economist, Ricardo Lopez Murphy.
Mrs Kirchner's critics have attacked her for failing to outline exactly what her policies are but voters who spoke to the BBC's Will Grant in Buenos Aires said the opposition had failed to offer any real alternative.
Just a few months ago, Mr Kirchner was riding high in the opinion polls and looked set to continue for a second term.
However, it was announced in July that his wife Cristina, senator for Buenos Aires province, would stand in his place. No explanation was given.
As candidate for the governing Front for Victory, she has promised to continue her husband's centre-left policies.
As well as facing comparisons with Eva Peron, Argentina's legendary former first lady, Mrs Kirchner has been compared to former US First Lady Hillary Clinton, who is also a lawyer and senator seeking to become the first elected female president of her country.
"I don't want to be compared with Hillary Clinton or with Evita Peron, or with anybody," she said recently.
"There's nothing better than being yourself."