Elections to the European Parliament are held every five years. The European Parliament was directly elected for the first time in 1979.
The last elections took place on Thursday 4 June 2009, when the UK's 72 MEPs were chosen. The newly-elected MEPs take their seats in the new Parliament on Tuesday 14 July 2009. The number of MEPs has been reduced from 78 as a result of the enlargement of the EU.
Since 1999 voters in Britain have elected MEPs under a proportional representation system. The European Parliamentary Elections Act of that year introduced a regional list system with seats allocated to parties in proportion to their share of the vote.
The UK is divided into twelve electoral regions with between three and ten MEPs representing each region. The nine English regions elected 59 MEPs, Scotland elected six MEPs and Wales four MEPs. In Northern Ireland three MEPs were elected under its own system of proportional representation.
All 736 MEPs in the European Parliament are elected under some form of proportional representation. Differences exist between Member States for example in the methods used (eg. Droop quota, d'Hondt system, Single Transferable Vote) or in the constituency unit (regional or national).