Millions of voters are casting ballots across Egypt to choose a new president, for the second time in two years.
A huge security operation has been mounted by police and the military, amid fear of attacks by militants seeking to disrupt the polls.
Former army chief Abdul Fattah al-Sisi, who deposed Islamist President Mohammed Morsi last year, is standing against left-wing candidate Hamdeen Sabahi.
Mr Sisi is forecast to win by a comfortable margin.
The elections are being held across two days, with unofficial results expected hours after polls close.
In Cairo, voters were queuing to cast their ballots almost an hour before polling stations opened, as military helicopters hovered overhead.
"We want security first, then everything else will follow," Manal Mohammed, a voter in the district of Imbabah, told the Associated Press.
More than 250,000 members of the security forces are on duty at polling stations across the country, according to the interior ministry.
The tight security drums home a familiar message from the military-backed interim authorities - that the dangers of Islamist militants are ever present, our correspondent says.
Militants have killed hundreds of security personnel since the army overthrew the president last July following mass opposition protests.
The militants say they have stepped up attacks in response to the state's subsequent crackdown on Mr Morsi's Muslim Brotherhood, in which more than 1,400 people have been killed and 16,000 detained.
Mr Morsi is currently standing trial on a raft of charges. He strongly denies any wrongdoing.
Islamists and some secular activists are boycotting the polls in protest at the clampdown and repression of dissent.
In his election campaign, Mr Sisi set out plans to develop agriculture, housing, education, impoverished areas and employment.
He is backed by several big businessmen as well as a broad range of political parties from the Islamist right to the moderate left.
Hamdeen Sabahi, who came third in presidential elections in 2012, offers an alternative to young voters who favour a civilian candidate over a former military one.
He promises to combat corruption and incompetence while promoting civil rights.
Both candidates say they will not re-legalise the Muslim Brotherhood.
Source/Fuente: http://www.bbc.co.uk/news/world-middle-east-27570653
