Egyptians began lining up at polling stations early Wednesday morning in the nation's first free elections since the downfall of Hosni Mubarak's 31-year regime in January 2011.
Officials are predicting a probable runoff on June 16-17 between the top two winners in the field of 12 candidates vying for the presidency.
The faceoff appears to be between two leading Islamists -- the Muslim Brotherhood's Abdel Moneim Abol Fotouh and Mohamed Mursi -- and the two secular front-runners, former Arab League head Amr Moussa and former prime minister and air force chief Ahmed Shafiq.
The winning candidate will be announced on June 21 and 10 days later, the interim government will hand over power to the new president.
With the Brotherhood and the Salafist al-Nour Party together holding a 70 percent majority in the upper and lower houses of parliament, some analysts are predicting an Islamist president could win the popular vote.
Since Mubarak's fall from power, the fate of Israel's 33-year peace treaty with Egypt has been bandied about, with Islamists threatening to re-examine which parts of the treaty might be left intact.
The most recent poll showed that more than 85 percent of Egyptians reject any normalization with Israel, while 90 percent prefer peace to war.