Presidential candidate Raila Odinga casts his vote in the Kenyan capital Nairobi.
He is one of the frontrunners in the Monday polls that have already been marred by violence following attacks that have killed at least 15 in Kenya's eastern coastal region.
Observers are hoping Kenya can avoid tribal bloodshed that marred elections in 2007 where 1,200 people were killed.
Meanwhile, main opponent Uhuru Kenyatta cast his ballot with his mother in the city of Gatundu.
He and his running mate William Ruto have been indicted by the International Criminal Court for orchestrating the 2007 violence, although both refute the charges.
Kenyatta said he was confident that Kenyans would choose a leader that brought the country together.
Ruto, who voted in Eldoret, said he and Kenyatta were working to clear their names.
(SOUNDBITE) (English) KENYAN DEPUTY PRESIDENTIAL CANDIDATE, WILLIAM RUTO, SAYING:
"I think we will comfortably be able to deal with our
