Socialist Bolivian presidential candidate Evo Morales appears to have won 50 percent of the vote in Sunday's election.
Mr. Morales' rivals, including conservative Jorge Quiroga, have already conceded defeat.
Mr. Morales spoke before a large crowd of cheering supporters in the town of Cochabamba, his political stronghold, saying a new history of Bolivia has begun.
The first official returns are expected later Monday. If Mr. Morales fails to win half the vote, Bolivia's Congress will choose the next president from the top two finishers.
Morales, 46, has vowed to reverse the U.S.-backed campaign to eradicate coca, the main ingredient in cocaine, but also used by Bolivia's Indians as a traditional medicine. Mr. Morales also wants to increase government control over Bolivia's natural gas resources.
Some information for this story provided by Reuters and AP.