The Assembly is made up of 60 Assembly Members (known as AMs), elected by the Additional Member System, a form of proportional representation. Elections are normally held every four years on the first Thursday in May. Anyone who can stand for election to the House of Commons may stand for election to the Welsh Assembly. Peers may also stand.
Each voter has two votes - one for a constituency member and one for a member from a regional list.
For the first vote, Wales is divided into 40 single member constituencies, which are the same as those for UK general elections. Voting is the same as in UK general elections using the first-past-the-post system in which the candidate with the most votes, though not necessarily the majority of votes, returned as an AM.
The second vote is more complicated. Wales is split into five regions made up of between seven and nine of the single member constituencies - North Wales, Mid & West Wales, South Wales Central, South Wales East and South Wales West. Each region returns four AMs. Before the election each political party has chosen a list of candidates in each region. A candidate in a single member constituency can be on a party's list for a region. Candidates on a party's regional list are arranged in the party's order of preference, with the candidate that the party would most like to see elected placed first.
In the second vote, votes are cast for parties. The number of AMs returned for each party in each region is shared out in proportion to the share of the vote received by each party. If a candidate on a party's list has already been returned in a single member constituency, the next candidate on the list is successful. Parties use this 'closed' list system as a form of insurance policy to ensure that key candidates have a better chance.
If a constituency member resigns or dies, then a by-election is held. If a regional member resigns or dies then the vacant seat is taken by the next person on the regional list for that party.
The Queen, normally accompanied by the Prince of Wales, officially opens the Assembly after each election but her address is not a 'Queen's Speech' in the Westminster sense - the First Minister outlines the Assembly business programme in an annual speech. A Presiding Officer is elected by AMs at the first meeting after an election.
The first elections to the Assembly were held on 6 May 1999. Further elections were held on 1 May 2003. The first plenary session of the National Assembly for Wales was held on 12 May 1999.