Malawians are going to the polls to elect a new president in what has been described as one of the country's most unpredictable elections.
There are seven candidates, but three are seen as having a realistic chance.
President Peter Mutharika is running for a second term, but he is being challenged by his own vice-president, Saulos Chilima, and Lazarus Chakwera.
The southern African country returned to multi-party elections in 1994 after 30 years of authoritarian rule.
The winning candidate just needs to get the largest share of the votes cast rather than more than 50%. Mr Mutharika won the last election in 2014 with 36.4%.
Who are the main candidates?
- Lazarus Chakwera - Malawi Congress Party - hoping to revive the fortunes of the former ruling party
- Saulos Chilima - UTM Party - current vice-president running against his boss
- Peter Mutharika - Democratic Progressive Party - current president running for a second term
The nearly seven million registered voters are also electing a new parliament and local councillors.
More than half of those who have registered are under the age of 34 and the youth vote may become a significant factor.
At the scene: Emmanuel Igunza, BBC News
There have been long queues at polling stations across the country.
Many of the voters turned up before dawn, hoping to vote early and go back to work. Voting day is not a public holiday in Malawi.
At the tax office polling station in the commercial capital, Blantyre, voting started nearly half an hour late, angering hundreds who had come early.
When I arrived 20 minutes before polls opened, electoral officials were scrambling to set up the voting stations.
People voiced their frustration at the electoral commission chairperson, who was at the centre to oversee the start of voting.
She managed to calm the crowd, and voting has been going on smoothly, albeit slowly. Delays have also been reported in other polling stations in the country.
Mr Chilima, who is 46, left the president's Democratic Progressive Party (DPP) last year after he fell out with Mr Mutharika after his fitness to run for office, at the age of 78, was questioned.
He has tried to appeal to young people in the promises he has made about addressing unemployment. Critics have said he will not be able to create one million jobs in his first year in office as he promised.
On election day, Mr Chilima was initially unable to vote at his polling station in Lilongwe, the Malawian capital, as his name was not on the register.
According to the electoral commission, Mr Chilima's name had been transferred to Chizumulu Island in Likoma district. He was eventually able to cast his ballot after contacting officials.
Mr Chakwera, 64, is the candidate for the resurgent Malawi Congress Party (MCP) - the official opposition.
The MCP led Malawi to independence in 1964 and governed the country as the sole legitimate party for three decades. But it has been out of power since multi-party politics returned 25 years ago.
Election in numbers :Â
6.9 million registered voters
54% of them are between the ages of 18 and 34
56% of registered voters are female
All 7 presidential candidates are male
More than 5,000 polling stations across the country
Polls open for 12 hours from 06:00 local time (04:00 GMT)
Violet Moyo, a businesswoman waiting to vote in Lilongwe, told AFP news agency that she was "super excited" to be casting her ballot.
"We have been disappointed so many times before but now we want something different," she said.
With high levels of poverty the economy, and in particular the state of agriculture, has been a big issue.
The government has been praised for the farm-input subsidy programme to help poor farmers but opposition parties say it has been fraught with corruption, another major issue on the campaign trail.
Polls opened at 06:00 local time (04:00 GMT) and close 12 hours later. The electoral commission has eight days to announce the result, but correspondents say it could be known as early as Wednesday evening.
Source : BBC