7 October 2012
Last updated at 22:39
Queues formed early outside polling stations in Caracas on Sunday. This is the fourth election contested by President Hugo Chavez, who came to power in 1998.
Almost 19 million Venezuelans are eligible to cast ballots. These voters are checking lists at polling stations for their names.
From Saturday evening to Monday evening, the sale of alcohol is banned and only the security forces are allowed to carry arms.
Mr Chavez, seen here gesturing to supporters after voting in Caracas, says he needs a fourth term to complete his "Bolivarian revolution" towards socialism.
Opposition candidate Henrique Capriles, who also voted in Caracas, accuses Mr Chavez of authoritarianism, suppressing the judiciary and silencing critics in the media.
This election is the most closely fought since Mr Chavez came to power.
Thousands of Venezuelans abroad voted at diplomatic missions around the world. Rebecca Ayana in London said she was voting for Mr Capriles.
Mr Chavez' supporters credit him with using Venezuela's oil wealth to improve health care, education and social housing.
Almost 140,000 soldiers have been deployed to guard more than 10,000 voting centres.
Voting is due to finish at 18:00 local time (22:30 GMT), but officials have said they will keep polling stations open if there are still queues at closing time.