A leftist candidate from one of Bolivia's Indian peoples who wants to legalise coca-growing has claimed victory in the presidential election.
Morales supporters have already begun celebrating in La Paz
"We have won," Evo Morales told thousands of cheering supporters as some exit polls suggested he had passed the 50% barrier for outright victory.
Earlier exit polls gave him 42% to 45% of the vote - still far ahead of former President Jorge Quiroga.
Mr Quiroga has admitted defeat and offered Mr Morales his congratulations.
As well as a president, Bolivia elected a new parliament, or Congress, and regional governors on Sunday.
Under Bolivian election rules, if no candidate polls 50% of the vote, the election does not go to a run-off but is decided by Congress instead.
But the leftist candidate seems certain to be confirmed as Bolivia's first indigenous president, whether through the official result or when MPs gather in several weeks' time.
'Finally in power'
Seconds after the first exit polls went out, celebrations could be heard in El Alto, the town high in the mountains around La Paz where support for Evo Morales is strong.
In a speech, Mr Morales said: "We have won and now we are going to change this country. All the majority together. The people are finally in power."
He said his political party, the Movement towards Socialism (Mas), would never "extort" foreign investors.
What many Bolivians had been dreading was a close vote, leaving Congress the almost impossible decision of whom to choose for president, the BBC's Daniel Schweimler reports.
The third-place candidate, businessman Samuel Doria Medina, has already said he will support in Congress whichever of the two front-runners receives the most votes at the ballot boxes.
It appears that Mr Morales, as well as surpassing expectations in his own strongholds, did well in Jorge Quiroga's home city, the business centre Santa Cruz
The television pictures tell the story, our correspondent says: long faces in the Quiroga camp and wild celebrations among the Evo Morales' supporters.
However, tens of thousands of people complained their names did not appear on electoral registers and their complaints are being investigated.
Bolivia, South America's poorest state, has had five presidents in four years.
Mr Morales, a former coca leaf-grower and union leader, described himself on election day as "the candidate of those despised in Bolivian history, the candidate of the most disdained, discriminated against".
Bolivia's indigenous people, who make up more than half the population, generally support the man who pledges to legalise the production of the coca leaf - which has traditional uses - although not the cocaine manufactured from it.
He also promises to make foreign oil and gas investors pay what he says is a fairer share to Bolivians.
Washington has said it expects any future Bolivian government to honour previous commitments to fight the production of illegal drugs.
Mr Morales, an admirer of Fidel Castro, said on Sunday that he wanted ties with the US but "not a relationship of submission".