France has reported record turnouts as voters choose between socialist Segolene Royal and conservative Nicolas Sarkozy for their next president.
Nearly 44 million French people are eligible to vote
In a hotly contested poll, nearly 75% of voters had cast their ballots by late afternoon - the highest turnout at that point in more than 30 years.
The winner will take over from Jacques Chirac after his 12 years in power.
Ms Royal has said a Sarkozy victory might spark riots, while Mr Sarkozy has accused her of verbal violence.
Polls opened at 0800 (0600 GMT) for mainland France's 43.5 million voters and are due to close at 2000 (1800 GMT).
One million citizens living in the overseas territories or other countries cast their votes earlier.
The first round brought 85% of the electorate out to vote, the highest turnout for 40 years.
Mr Sarkozy voted in his home of Neuilly-sur-Seine near Paris, accompanied by his two step-daughters - though not his wife Cecilia.
He was greeted by supporters who applauded him and chanted "Sarko president!".
Ms Royal cast her vote in her constituency in the Poitou-Charente region, though she is expected back in Paris for a post-result speech.
At a polling station near the Champs-Elysees in Paris, unemployed voter Anne Combemale said she had chosen Mr Sarkozy because of his market-oriented economic platform.
"He has the willpower to change France," the 43-year-old said.
In Argenteuil, the town north-west of Paris where Mr Sarkozy notoriously talked of hosing out "rabble" before the 2005 urban riots, Doratine Ekoka, a 70-year-old retired computer programmer, said she trusted Ms Royal to "clean up public life".
A Sarkozy victory, she added, "would be like a punishment from God" because of his "terrible character".
More than 3,000 police have been deployed in Paris and its multi-ethnic suburbs to prevent a repeat of the 2005 riots if, as many expect, Nicolas Sarkozy celebrates a victory on Sunday night.
The BBC's Caroline Wyatt in Paris says there is almost a sense of relief among many that after months of campaigning and heated debate, the nation is finally making its choice about the future.
Whoever wins, it will mark a generational shift, with power being handed over by 74-year-old Jacques Chirac to a new president in his or her fifties.
Mr Sarkozy is a tough former interior minister who has promised reforms to put France bring down high unemployment and boost economic growth.
Ms Royal has also pledged to create new jobs, while keeping France's cherished social model of generous welfare benefits and state aid.
The winner will inherit a fractured society in need of both economic reform and a new self-confidence, as France seeks to regain its former economic strength and its global influence, our correspondent says