The way in which people in Northern Ireland will vote in the election differs from the rest of the UK. The province will use the single transferable vote (STV), as it does for local councils and most regional-level elections.
The regions in Britain use a simple form of list proportional representation. Electors have one vote and may vote either for a party or for an individual candidate.
Each political party prepares a list of candidates to match the number of seats to be filled in each region. If the party wins two seats in a region their top two candidates on the list will fill these seats.
In each region, each party wins a share of the seats which roughly matches the share of votes each party gets.
In Northern Ireland, STV will be used for the election. It is a system of proportional representation.
The system allows voters to vote for individual candidates (as opposed to party lists) in order of their choice,
both between parties and within parties.
The votes are then transferred, if necessary, from candidates who have either been comfortably elected or who have done so badly that they are eliminated from the election.
Counting of votes in the Single Transferable Vote (STV) system involves a number of 'stages':
3 The exclusion of one or more candidates at any given time.
The returning officer sorts the ballot papers into parcels according to the candidates for whom the first preference votes are given.
The numbers of first preference votes given to each candidate are recorded, along with the total number of valid ballot papers.
The total number of valid ballot papers are then divided by the number of members to be elected plus one.
As there are to be three members to be returned to the electoral region of Northern Ireland, the total number of valid ballot papers will be divided by four.
This number plus one is the quota, that is the number of votes sufficient to secure the election of a candidate.
At any stage in the count, when the total number of votes for a candidate equals or exceeds the quota, the candidate in question is deemed to be elected.
Where the first preference votes for any candidate exceeds the quota, all ballot papers on which first preference votes are given for that candidate are sorted into sub-parcels.
These are grouped according to the next available preference given on those papers for any continuing candidate.
Where no further preference is given, the ballot papers are grouped as non-transferable votes.
Each sub-parcel of transferable ballot papers is then transferred to the candidate for whom the next available preference has been given on those papers.
The value of these votes, the 'transfer value' is calculated so that their total value is not greater than the surplus of the elected candidate.
The total number of votes for each remaining candidate is recalculated, and where the number of votes for any candidate exceeds the quota, the candidate in question is deemed to be elected.
This process is repeated in a series of stages, continuing until all surplus voting papers have been transferred.
If one or more vacancies remain to be filled, candidates with the least votes are excluded in turn. Consequential surpluses are transferred as they arise until the desired number of candidates has been deemed to be elected.
On the exclusion of a candidate, or transfer of a consequential surplus, any candidate attaining or exceeding the quota is deemed to be elected.
Each transfer of a surplus or exclusion of a candidate constitutes a further stage in the count.
In the United Kingdom 87 Members of the European Parliament (MEPs), including three from Northern Ireland, were elected at the last round of election in 1999.
Members of the European Parliament have been directly elected since 1979 and there have been elections every five years since then.
UK MEPs are elected on a regional basis to 12 electoral regions: Scotland, Wales, Northern Ireland and 9 regions in England with the number of MEPs being roughly in proportion to the size of the population in each region.
Voting takes place on 10 June
The five elections to date have produced very similar results, with the DUP (Ian Paisley Sr), SDLP (John Hume) and UUP (John Taylor, now Lord Kilclooney, in 1979 and 1984, Jim Nicholson in 1989, 1994 and 1999) taking one seat each at every election.
As both Mr Paisley and Mr Hume have announced their retirement from the European Parliament, the 2004 election is likely to be the most open European election in Northern Ireland since 1979.
A total of 626 members were elected across the EU in 1999.
With the accession of 10 new members to the EU on 1 May 2004 the total number of MEPs will be increased to 732 and the numbers of MEPs allocated to each existing member state will be reduced.
The UK number will be reduced from 87 to 78. The number of MEPs was reduced by one in each of 10 of the 12 UK regions excluding Northern Ireland and the East Midlands.