The richest man in Ecuador is to face a leftist in a run-off next month after the first round of the presidential election, partial results make clear.
Mr Noboa has promised to sign a free trade pact with the US
Banana tycoon Alvaro Noboa won slightly more of the vote than Rafael Correa, a left-wing ally of Venezuelan President Hugo Chavez.
The outgoing President, Alfredo Palacio, described the election as a festival of democracy.
Ecuador is electing its eighth leader in a decade of political turbulence.
With about 70% of the votes counted Mr Noboa had 26.7% of the vote compared to 22.5% for Mr Correa.
The second round will be held on 26 November.
It looks like being the result most analysts in Ecuador had predicted, the BBC's Daniel Schweimler reports from Quito, but Mr Correa, a 43-year-old economist, was quick to claim fraud and that he had won an outright victory.
Mr Correa has vowed to challenge the political establishment
He said attempts had been made to bribe his party workers in some areas and that he would be making a formal complaint.
Alvaro Noboa, who at 55 is trying for the third time to become president, said he was pleased with the result and looked forward to the second round.
"I am deeply touched," he told a rally of supporters.
"It has been my struggle since 1998. They took it away from me in 1998 and in 2002... I have just checked again with the Supreme Electoral Tribunal and I am in first place."
The two men could not be more different, our correspondent notes.
Mr Noboa inherited his father's banana empire and enjoys much of his support in Ecuador's financial centre, the coastal city of Guayaquil.
Mr Correa is a friend of Mr Chavez and he has said he would oppose a planned free trade deal with the US.
He enjoys the bulk of his support in Quito.
Many people in Ecuador are already disillusioned with their politicians, our correspondent says.
The fight between Rafael Correa and Alvaro Noboa may not be a pretty one and is unlikely to restore much faith in the country's politicians, he adds.
Ecuadoreans drove their last three elected presidents from power and only three since 1979 have succeeded in serving full terms.