The presidential election in Serbia has been won by the pro-Western candidate of the Democratic Party, Boris Tadic.
Tadic said the poll showed there was no turning back for Serbia
His rival in the run-off poll, Tomislav Nikolic of the nationalist Serbian Radical Party, has admitted defeat.
Previous three ballots were declared invalid because of a now abolished law that required a minimum turnout of 50%.
According to final estimates from the Centre for Free and Fair Elections, Mr Tadic won 53.7%, with Mr Nikolic polling 45%. Turnout was about 49%.
"This election has shown that Serbia knows how to recognise a historic moment," Mr Tadic, 46, said as he celebrated his victory.
He said the poll "showed that there is no turning back from October 2000" - referring to when Slobodan Milosevic was ousted from power.
Mr Nikolic congratulated Mr Tadic, saying he was "satisfied" with the results.
Mr Tadic, who polled lower in the first round, has benefited from the support of other Democratic parties, including that of the current prime minister, Vojislav Kostunica, the BBC's Matt Prodger in Belgrade says.
The preliminary results appeared to signal a desire by Serbs to move closer to the European Union and Nato and away from the nationalist isolation during Slobodan Milosevic's years in power, analysts say.
However, Mr Nikolic's 45% shows that Serbia has decided but still remains divided, our correspondent says.
Nikolic believes in a "Greater Serbia"
Official results are not expected until Monday.
Serbia has been without a president since 2002 when Milan Milutinovic left office and was sent to The Hague to face war crimes charges.
Mr Tadic - a soft-spoken psychologist - represents the reformist movement in Serbian politics which helped topple Slobodan Milosevic in 2000, while Mr Nikolic, 52, criticises the post-Milosevic period of democracy.
Mr Nikolic's Serbian Radical Party is headed by Vojislav Seselj who is awaiting trial in The Hague on war crimes charges.
Mr Nikolic believes in a "Greater Serbia" encompassing land in neighbouring Bosnia and Croatia, although he now says that should be achieved peacefully.
"I'll dream about that border as long as I live," Mr Nikolic said last week.
The two men came top in the first round of voting earlier two weeks ago, knocking 13 other candidates out of the race.