KABUL (Reuters) - Voting was under way in Afghanistan's presidential election on Saturday, with about 12 million people eligible to choose between eight candidates.
Here are brief descriptions of the three leading contenders.
ASHRAF GHANI AHMADZAI
The American-trained anthropologist returned to Afghanistan after the Taliban were ousted and held various government posts, including finance minister. Known in Afghanistan as Doctor Ashraf Ghani, he won about four percent of the vote in the last presidential election in 2009.
One of Afghanistan's best-known intellectuals, Ghani spent almost a quarter of century abroad during the tumultuous decades of Soviet rule, civil war and the Taliban regime.
During that period he worked as an academic in the United States and Denmark, and with the World Bank and the United Nations across East and South Asia.
Within months of the September 11, 2001, attacks on the United States, Ghani resigned from his international posts and returned to Afghanistan to become a senior adviser to Karzai.
Ghani is among the strongest backers of a crucial bilateral security deal to keep U.S. troops in Afghanistan beyond 2014 that Karzai has refused to endorse. He has said he would sign it swiftly if elected.
A Pashtun belonging to Afghanistan's biggest ethnic group, Ghani has defended his decision to pick ethnic Uzbek former warlord Abdul Rashid Dostum as a running mate.
"The ticket is a realistic balance between forces that have been produced in the last 30 years and have a base in this society," Ghani told Reuters.
The former foreign minister has been one of Karzai's closest confidants.
His colleagues know him as a calm and soft-spoken statesman, who over his three years in the job accompanied Karzai on his official visits overseas.
Rassoul also held roles in national security, being close to the president since the early days of his government, when Karzai was plucked from obscurity by the United states to lead Afghanistan after the Taliban were ousted in 2001.
Critics say that, if elected, Rassoul - born in 1943 in a reputed Pashtun family in Kabul - would lack the strength and independence to make a break from the old administration, which has been accused of perpetuating a culture of corruption and inefficiency.
A former ophthalmologist-turned-fighter of Soviet forces in the 1980s, Abdullah dropped out of a run-off against Karzai in the 2009 election, citing concerns about mass electoral fraud.
An adviser to the late guerrilla leader Ahmad Shah Masood, Abdullah was foreign minister until his abrupt dismissal in 2006.
Abdullah's base of support is in the ethnic Tajik community and, although he is half-Pashtun, he is best known for championing the causes and rights of Afghanistan's second-largest ethnic group, Afghan Tajiks.
As a young man, Abdullah studied medicine at Kabul University and worked as an ophthalmologist until 1985.
A year later he joined the Panjshir Resistance Front against the Soviets and served as an adviser to Masood, a national hero for many Afghans.
Abdullah was foreign minister of the United Front - better known internationally as the Northern Alliance - from 1998 and, after Masood's assassination in 2001, became a dominant figure in the alliance that helped U.S. forces topple the Taliban.
(Compiled by Kabul newsroom; Editing by John Chalmers and Clarence Fernandez)