The ANC is under fire from supporters who are demanding better housing and basic services.
Despite increasing criticism and angry protests for failing to provide housing, electricity, proper sanitation and tap water the ANC looks certain to win the elections.
"Every country in the world faces challenges. One of our challenges here is to ensure that we deal with poverty, lack of education," said Nelson Mandela, South Africa's first black president, as he cast his ballot in Johannesburg.
"I voted for myself," the frail-looking Mandela said jokingly, wearing an AIDS ribbon and one of his trademark African-style shirts. "Even if I go to my grave, I will wake up and come and vote."
Polling stations closed at 7:00 pm (1500 GMT) and voting went fairly smoothly across the country although one community boycotted the elections to protest a boundary change residents believe will result in fewer services.
Fears that voters would stay away in the rest of the country appeared to be unfounded as the Independent Elections Commission reported that early indications showed "a very good turnout."
Early results showed increased support for the opposition Democratic Alliance from a small town in the Eastern Cape province.
Ballot counting was under way at polling stations across the country and the final results are only expected at the weekend.
Voter turnout figures were not yet available but political analyst Hennie Kotze said he expected it to be around 40 percent.
The ANC has been cruising from victory to victory in elections since it swept to power under Mandela in the first multi-racial ballot 12 years ago, but it has faced an unprecedented level of voter anger in the campaign.
Unemployment stands at 26 percent and more than half of the 46-million population lives below the breadline.
The ANC has also been plagued by infighting since President Thabo Mbeki fired his former deputy president Jacob Zuma, who is facing corruption and rape charges.