Q&A: Pakistan's parliamentary elections
Voters in Pakistan have taken part in general and provincial elections.
The election to the National Assembly (NA) will mark the first successful transition from one democratically elected parliament to another in the country's 66-year history.
How important are the elections?
The vote is a big test for Pakistan's democracy.
The new assemblies will elect the next prime minister and the chief ministers of the four provinces. The outcome will also have a bearing on the fate of President Asif Ali Zardari, whose term in office ends later this year.
The president is elected by members of the National Assembly, the four provincial assemblies and the Senate.
Who are the main players?
President Zardari's Pakistan People's Party (PPP) is the dominant force in the outgoing federal government but few expect it to perform as well as in 2008 , after its leader Benazir Bhutto had been assassinated.
The main opposition parties are the Pakistan Muslim League (PML-N) of ex-Prime Minister Nawaz Sharif, seen as favourite to win the elections, and the Pakistan Tehrik-i-Insaaf (PTI) of cricketer-turned-politician Imran Khan. His party is also expected to perform strongly.
The Pakistan Muslim League Quaid-i-Azam (PML-Q) is part of the outgoing governing coalition and has formed an informal electoral alliance with the PPP in Punjab, the country's most populous province.
The secular Muttahida Qaumi Movement (MQM), which is popular among urban voters and the business community in Karachi and Hyderabad, is a coalition partner of the PPP at the federal level and in Sindh province. It has, however, fielded its own candidates in all four provinces and has not sought any electoral alliances.
The secular Awami National Party (ANP) was in coalition with the outgoing PPP government federally and in Khyber Pakhtunkhwa province but is also going solo in the 11 May polls.
What about religious parties?
Several religious parties have fielded candidates in different parts of the country.
The Jamiat Ulema-i-Islam-Fazal (JUI-F) is a right-wing party with ideological links to the Deobandi orientation of Islam. It has eight seats in the outgoing National Assembly and seven in the Senate and is considered to be the most important religious party in the elections.
It has formed an informal electoral alliance with a secular party in parts of Khyber Pakhtunkhwa province.
Jamaat-i-Islami (JI), the oldest religious party in Pakistan, boycotted the 2008 elections in protest at former military ruler Pervez Musharraf, but it has fielded some strong candidates in Punjab, Khyber Pakhtunkhwa and Sindh.
Five other religious parties are participating in the 11 May polls under the banner of the Mutahida Deeni Mahaz (United Religious Front).
These include Ahle Sunnat Wal Jamaat (ASWJ), seen in Pakistan as the political face of Lashkar-e-Jhangvi (LeJ), a militant group which has been blamed for killing hundreds of Hazaras in Quetta and other Shia Muslims in other parts of the country.
ASWJ leader Maulana Ludhianvi is contesting a National Assembly seat in Jhang district, which he lost to a PML-Q candidate in the 2008 elections.
What are the main issues?
There is no single dominant issue in these elections.
The PML-N and PTI have campaigned on power shortages and alleged corruption in the outgoing government, while religious parties are trying to exploit anti-US feelings by focusing on drone attacks.
Possible talks with Taliban militants to end the current wave of violence are another subject of debate at rallies and in talk shows.
Will the voting be free and fair?
The public has high hopes for the polls as, for the first time, they will be supervised by a powerful election body on which the government and the opposition reached consensus.
This body has so far maintained a neutral image while dealing with different issues that have cropped up during the campaign.
However, leaders and workers of the PPP, MQM and ANP, which are all part of the outgoing government, have been the targets of a series of bomb attacks blamed on Taliban militants. The parties have been unable to campaign normally as a result.
The leaders of these parties say the failure of law enforcement agencies to ensure security as a case of pre-election vote-rigging.
What is at stake for the international community?
The presence of Nato forces in Afghanistan and their scheduled exit next year via Pakistan, as well as the role played by Pakistan in the fight against terrorism, means that the international community is watching developments in Pakistan very closely.
Observers say a strong government led by Nawaz Sharif could be a major concern for Nato forces fighting Taliban militants in Afghanistan.
Mr Sharif is close to right-wing religious forces in Pakistan who oppose US policy, and he has an uneasy relationship with the Pakistani military which unseated him in a 1999 coup.
The European Union has sent as many as 110 election monitors. The US-based National Democratic Institute is assembling a team of 57 short and long-term observers.
Several governments, including the United States, Japan and Turkey, are also expected to send observers to oversee the poll.