The candidates have spoken at large rallies all over Yemen
Yemenis go to the polls on Wednesday to choose a president for the next seven years, with incumbent Ali Abdullah Saleh facing a serious challenge for the first time since taking charge following the country's unification in 1990.
Voters will also be casting their ballots in local assembly elections.
Who's in power at the moment?
President Ali Abdullah Saleh is the only head of state unified Yemen has ever known. He has been president since unification in 1990, and governed the former Yemen Arab Republic (YAR) for 12 years before that.
Now 64, Mr Saleh joined the army when he was 16, and was among a group of officers who successfully staged a coup in 1962. He then climbed up the political ladder before taking over in the YAR in 1978.
He is campaigning on a platform of national unity, security and stability.
Who else is running for president?
The main challenge to Mr Saleh comes from Faisal Bin Shamlan, who has been a fixture in Yemeni politics for more than 40 years and is the main opposition candidate.
Since returning to Yemen after studying in Britain in the 1960s, he has spent time as an MP as well as serving in a number of high-ranking posts, including a short stint as oil minister in the mid-1990s.
The election programme set out by the 72-year-old focuses on political and economic reforms, good governance and fighting corruption.
Three other men are standing for president, although none of them are expected to have a significant impact on the result.
What are the key issues?
Mr Saleh originally vowed not to stand in these elections, but then reversed his decision.
He said he was responding to an appeal from the Yemeni people, and has since predicted that the vote will make a peaceful transition of power easier in the future.
However, the opposition has accused him of trying to preserve a "monopoly of power", and Mr Shamlan has promised to install a parliamentary democracy if he wins.
Economic issues have also played an important part in the campaign.
Despite access to oil and gas reserves, Yemen remains one of the poorest countries in the Arab world, something the opposition attributes to economic mismanagement and government corruption.
Mr Saleh counters that any "great progress" inevitably has its flaws.
The recent abduction of four French hostages by southern tribes, the government's claim to have foiled an attack on oil installations and major unrest during the campaign have also highlighted the problems of maintaining security.
This has been exacerbated by the government's inability to extend its writ over tribes based in rural areas, where the rate of private gun ownership is one of the highest in the world.
Which are the main parties?
Yemen boasts some 40 political parties, but few of them have any representation in parliament.
The dominant player in the party system is the ruling General People's Congress (GPC), which was founded by Mr Saleh in the 1980s as an "umbrella for all social forces", especially from the political and military establishment in North Yemen.
It enjoyed success in elections before unification, initially shared power afterwards and is still led by the president.
Mr Shamlan is backed by the Joint Meeting Parties (JMP), an alliance of five opposition parties.
The JMP, which is campaigning for good governance, includes Islah, Yemen's main Islamist party and its best-organised opposition group.
Among its other members is the Yemeni Socialist Party, which once governed the former People's Democratic Republic of Yemen, but has lost much of its influence since unification.
Who can vote?
Yemen has a population of more than 21 million, and some 9.3 million of them are eligible to vote in the polls.
Those who wish to vote must register to do so, and must be aged 18 or over to take part. Voting is voluntary and conducted through secret ballot.
Yemenis living outside the country are also allowed to vote.
Who supervises the voting?
The elections will be overseen by the Supreme Commission of Elections and Referendums (SCER).
Yemen's Supreme Court is the final court of appeal for any issues relating to the elections.
Nearly 90,000 police and soldiers will be deployed to maintain law and order.
Will there be observers?
The European Union, the US and Canada are each sending teams of observers to monitor the elections.
Both the president and SCER have been vocal in endorsing their presence.
Mr Saleh said in a national address at the start of August that Yemen was keen to welcome observers in order to "appear civilised and cultured".
However, election officials have voiced concern for the security of those observers.
What happened last time round?
Yemen last held a presidential election on 23 September 1999, the first direct vote of its kind on the Arabian Peninsula.
Mr Saleh won the vote by a landslide against his sole challenger, a GPC member running as an independent candidate, gaining 96% of the ballots cast.
BBC Monitoring selects and translates news from radio, television, press, news agencies and the internet from 150 countries in more than 70 languages. It is based in Caversham, UK, and has several bureaux abroad.