Adam finds out what happens at the European Parliament
Every five years the UK picks members for the European Parliament, which is one of the main parts of the European Union, along with the European Commission and the European Council.
In 2009, the 72 UK MEPs who were elected joined 664 other MEPs from across the European Union (EU).
Together they formed a 736-member parliament, which aims to provide a voice for the people of the EU.
The smallest member state is Malta, with five MEPs, while the largest is Germany, with 99 MEPs.
The voting system is pretty complicated. Instead of voting for one candidate you vote for a political party.
The party then picks your MEP from a list it has drawn up.
The more votes your party gets, the more MEPs it can pick from its list.
Who can vote?
EU citizens over 18 who are registered to vote can take part in these elections.
What actually happens is that not many people bother to vote in the UK. This is called low turnout and it's also a problem in some other EU countries.
Why don't people vote?
There are lots of explanations. Some people say the voting system is too complicated. Others think the public don't know what the European Parliament does.
Arguments about the EU often make the news in the UK but opinion polls show that ordinary people see Europe as a less important issue than things like hospitals, schools and transport.
More recently, the row about British MPs' expenses means lots of people have lost faith in politics and don't see the point of voting.
So what does the European Parliament do?
It decides whether suggestions from the European Commission should be made into new laws.
It also helps to decide how much money the EU should spend and checks that all the other parts of the EU are working fairly.
Voting system in more detail
- The UK is divided into 12 regions
- Each region is given between three and 10 MEP seats
- The more people that live in a region - the more seats it gets
- For each of the regions the political parties submit a list of the candidates they think should be MEPs.
- Voters mark their ballot paper to show which party they want to win.
- The votes are counted and the region's seats are shared out between the parties - the more votes you got the more seats you get.
- Northern Ireland uses a different voting system.