Mr Aquino is the son of a beloved former president
Senator Benigno "Noynoy" Aquino moved closer to victory in the Philippine presidential election as an early front-runner conceded defeat.
Mr Aquino's colleague and rival for the presidency, Manny Villar, has congratulated him on his victory.
But no word has yet emerged from his closest rival, Joseph Estrada.
The Commission on Elections said Mr Aquino, son of two democracy icons, had about 40% of the vote to Mr Estrada's 25% with most districts counted.
A high turnout was recorded despite big delays caused by new voting machines.
Mr Aquino said if confirmed as president, he would use his position to tackle corruption and improve public health, education and the judiciary.
"I will not only not steal, but I'll have the corrupt arrested," he told a news conference in his home province of Tarlac.
The BBC's Kate McGeown in Manila says the initial results are so clear cut there appears to be little room for argument and Mr Aquino seems virtually certain to become president.
This is rare in a country where political squabbles have often led to uncertainty and violence, our correspondent adds.
Outgoing President Gloria Arroyo, who is standing down at the end of her second term in office as required by the constitution, has promised to make the handover of power as easy as possible.
"The true hallmark of a strong, functioning democracy is a smooth transition to a new government," she said.
"The people deserve to have their new leaders put aside politics and focus on the future and the business of governing."
Mrs Arroyo will hand over power on 30 June but was running for a seat in Congress - initial results indicated she was successful.
Two high-profile candidates running for posts - former first lady Imelda Marcos and world champion boxer Manny Pacquiao - also appeared to have won their seats.
Filipinos cast their ballots on Monday for a new president, vice-president and more than 17,000 other official posts.
Early indications showed Mr Aquino far in the lead. Mr Estrada had about 25.76% of the vote with Mr Villar, a property tycoon, trailing in third with just under 14%, said Commission on Elections (Comelec) chair Jose Melo.
Voting for president, vice-president and more than 17,000 officials
Some 50m registered voters
Presidential front-runners include Joseph Estrada, Benigno Aquino and Manny Villar
More than 90 people killed in pre-election violence
Problems reported with new automated voting machines
"The Filipino people have decided," Mr Villar told a news conference. "I congratulate Senator Noynoy Aquino for his victory."
"The challenges he and our country faces are enormous and we should work together."
Local television quoted a lawyer for Mr Estrada as saying that his team would probably seek to contest the results.
Mr Aquino had been the pre-election favourite.
Correspondents say the 50-year-old's political pedigree - as the son of the beloved former president - has been the secret of his success.
He is considered honest and well-intentioned despite his somewhat low-profile career as a legislator.
Speaking while votes were being counted, Mr Aquino vowed that if confirmed as president he would adhere to his election pledges.
"I will go back to my campaign slogan, government has lost its power to positively affect our people's lives because of corruption, therefore the first priority has to be address the issue of corruption," he said.
"Get government's power back so they can empower the people. And empower them in so many areas, like education, in health, in having a judicial system that works, and so on and so forth."
Mr Melo said that about 75% of the more than 50 million registered voters in the country had cast a ballot.
The election day was marred by deaths from political violence
Fears of widespread chaos resulting from the use of new automated voting machines failed to materialise.
The new machines did cause long delays but voters waited patiently for hours in the heat to vote.
Despite high security, voting was marred by the deaths of at least 12 people in political violence.
The deaths came after a bloody campaign period in which more than 30 people died. Another 57 died in a mass killing in November.
In the latest reported violence, the AFP news agency said communist insurgents had ambushed an election convoy in the south of the country, killing six people and wounding 12.