The presidential and parliamentary polls, the third held since the end of the 1991-2002 conflict, pit President Ernest Bai Koroma and his ruling All People's Congress (APC) against challenger Julius Maada Bio, a former junta leader who represents the Sierra Leone People's Party (SLPP).
Voters clutching plastic electoral cards jostled outside polling stations set up in schools and other public buildings in the steamy seaside capital Freetown and across the nation.
"I want to vote early and go back to my house. I want to go and sit down and listen to what is happening in the country," said Mariama Khellah, an unemployed 37-year old, as she waited outside St Luke's Primary School in western Freetown.
The elections are being held amid rising expectations foreign-run iron ore mining and oil developments can start lifting Sierra Leone's 5.5-million people out of poverty and help the country shed its image as a "blood diamonds" battleground for rebels and child soldiers.
The vote is expected to be close. Former insurance executive Koroma, 59, who wrested the presidency from the SLPP in a hotly disputed 2007 vote, is considered the narrow favourite, above Bio, a 48-year-old retired army brigadier who was involved in two military takeovers in the turbulent 1990s.
A turning point
To win outright, a candidate must gain 55% of the vote and the race may well go to a second round.
"I think the whole world is looking at Sierra Leone at the moment," said Jens Anders Toyberg-Frandzen, the United Nations envoy to the country. He called the vote "a turning point in manifesting that Sierra Leone has graduated from a post-conflict country to one that is now on the path to development."
The elections in the former British colony will be one of the most closely observed in Africa this year by monitors from the European Union, the Commonwealth and the African Union.
With rivalry between the APC and the SLPP running high, there are concerns a close result could ignite violence, although the election campaign saw only minor scuffles.
"Compared with our worst fears, it's been pretty good," said the EU's chief election observer, Richard Howitt.
At stake is the opportunity to oversee millions of dollars of investment in the aid-dependent country's resources that include gold and diamonds, oil and iron ore.
Iron ore shipments by British companies African Minerals and London Mining are expected to buoy the economy to 20% growth this year – below original forecasts of more than 50% but still one of the highest growth rates on the planet.
Doubts remain over whether the election winner can root out the graft from Sierra Leone's patronage-driven politics, fairly distribute the mineral wealth and unite the war-scarred society over tribal and political divisions.
In the electoral propaganda battle waged in Freetown's pot-holed streets, APC billboards have sought to emphasise Koroma's performance over the last five years in building new roads, improving the power supply and bringing in foreign investors.
De Pa Dea Woke (The Father is working) proclaims one pro-Koroma billboard in the local Krio language, while another assures voters the president's "Action Pass Intention".
SLPP posters hail Bio as a "Father of Democracy". His supporters point to his role in handing over to civilian rule more than a decade ago and rebuff accusations from critics who question his military past and democratic credentials.
Although ethnic allegiances still shape Sierra Leone's electoral landscape – Koroma's APC draws support from the Temne and Limba peoples of the north, while the Mende of the south and east traditionally vote SLPP – both candidates face pressure to convert the mineral riches into jobs and improved livelihoods.
Power of development
But a strong consensus also exists among voters that Sierra Leone must never be allowed to fall back into the violence of the brutal 1991-2002 war, when thousands of civilians had their limbs hacked off by drugged-up bush fighters.
"People are getting aware. People are no more interested in violence," said Alimany Barrie, a 45-year-old army corporal, as he lined up to vote in Freetown in civilian clothes.
"They have seen that the power of development is through the ballot box, not the bullet," he said.
Soldiers in crisp new green camouflage and floppy bush hats joined police in trying to control the impatient, shoving lines of voters, some of whom had waited through the night.
At one polling station in the capital's Cardiff Primary School, Fafata Kamara was squeezed in a crammed line of voters snaking down a dirt road, many women wearing colourful wraps and headscarves and carrying babies on their backs. "Let us have good leaders to develop the country," she said. – Reuters