Polls have closed in a South African election that posed the toughest challenge to the ANC since the end of apartheid.
The party looks assured of a fourth straight win since defeating white minority rule in 1994 under Nelson Mandela and will make its leader Jacob Zuma president.
But the party faces an unprecedented challenge from opposition parties hoping to capitalise on frustration over corruption, poverty and crime, and could lose the two-thirds majority that gives it the right to change the constitution.
Queues formed before dawn outside polling stations across the country.
The electoral body hoped voter turnout would top 80%, compared with 77% in 2004. Voting papers were running short in some areas.
Polls closed at 9pm (8pm Irish time) and first results were expected late tonight.
Many analysts believe the ANC, whose anti-apartheid credentials make it the choice for millions of black voters, will win 60-66% of the vote, compared to nearly 70% in 2004.
One consultancy predicted that the ANC is slightly more likely to lose its two-thirds parliamentary majority than to retain it, putting the chances at 55% versus 40%.
A smaller ANC majority would cheer investors keen to see its grip loosened. Despite Mr Zuma's assurances, they fear he may bow to leftist allies who say policies credited with South Africa's longest spell of growth have harmed the poor.
But with South Africa possibly in its first recession in 17 years and mines and factories hard hit by the global downturn, the room for policy change is limited.
Finance Minister Trevor Manuel, a market favourite, is expected to stay for now.
A key challenge to the ANC comes from a new party formed by those loyal to former President Thabo Mbeki, ousted by the ANC amid allegations he meddled in the corruption case against Mr Zuma, which was dropped this month.
The first credible black opposition party, the Congress of the People (COPE), has some support among the growing black middle class, but has struggled to win over the poor.
Presidential candidate Mvume Dandala said the new party was still optimistic it could bring change.
The official opposition Democratic Alliance, resurgent under new leader Helen Zille, a white South African, also hopes to boost its presence in parliament and has campaigned under a ‘Stop Zuma’ slogan, with an anti-corruption message.
A frail-looking Nelson Mandela, 90, smiled as he was helped up to a ballot box in Johannesburg.
One voting officer was arrested after marked ballot papers were found at a polling station, but there were no reports of major delays or disruption.
