![]() |
Nearly 5m people are eligible to vote in El Salvador, where more than a third live in poverty |
The governing party candidate - former rebel commander Salvador Sanchez Ceren - won the first round and has a comfortable lead in opinion polls.
His right-wing opponent, Norman Quijano, says the government has been too soft on street gangs responsible for much of El Salvador's violence.
The Central American nation has one of the world's highest murder rates.
In the first round, held on 2 February, Mr Sanchez Ceren had 48.93% of the vote. He needed 50% to avoid a run-off against Mr Quijano, who received 38.93%.
Mr Sanchez Ceren, 69, was a Farabundo Marti National Liberation Front (FMLN) commander during El Salvador's bloody civil war, which went on from 1980 to 1992.
The FMLN became a political party after the end of the civil war and won the presidential election for the first time in 2009.
Mauricio Funes was elected and Mr Sanchez Ceren served as his deputy.
Street gangs truce
In 2012, Mr Funes's government facilitated a truce between the country's two biggest gangs.
The criminal organisations, or "maras," are involved in drug trafficking, kidnapping and vicious turf wars in El Salvador and neighbouring countries.
The truce initially reduced El Salvador's murder rates but there are signs that the deal is falling apart.
Mr Sanchez Ceren has tried to distance his campaign from the plan, which is widely unpopular with ordinary Salvadorans, says the BBC's Will Grant.
He says he will try to include all political forces in the government if he wins the vote.
"The Salvadoran people want hope. For that reason, we are going to build a great national understanding with all political forces," said Mr Sanchez Ceren.
He has promised to tackle crime through education and social programmes.
Mr Quijano, 67, has blamed the government for negotiating with gang leaders.
Despite the high rates of violent crime and economic instability, Mr Quijano's Arena party has not been able to mount a serious challenge to Mr Sanchez Ceren.
Opinion polls show the governing candidate 10 to 18 percentage points ahead of his rival.
The new president will be sworn in on 1 June for a five-year term.