BBC staff have gone on strike - but why are they taking action and what will it mean for viewers and listeners?
Why are BBC staff striking?
Director general Mark Thompson is cutting 3,780 jobs at the corporation - almost one in five of its UK public service staff.
That involves 15% cuts across most departments - with some sections suffering greater losses and others less affected.
Mr Thompson has said the cuts are necessary to streamline the BBC and take it into a rapidly-changing hi-tech broadcasting environment.
The unions called the strike because the BBC did not rule out compulsory redundancies and said the corporation refused to enter into "meaningful negotiations".
How will it affect BBC programmes and services?
The BBC will do its best to keep a seamless service going - which may involve more pre-recorded and repeat programmes.
When ITV staff went on strike last month, executives recorded "live" shows in advance and used external companies and studios to cover striking staff.
BBC media correspondent Nick Higham said live programmes would be particularly affected, especially news - which cannot be prepared in advance.
If the unions are correct in their estimate of about 11,000 members supporting the strike, then Radio 4's Today programme, BBC2's Newsnight, Radio Five Live, and possibly coverage of the Chelsea Flower Show will be affected.
Nick Higham also added that a Paris concert by Oasis which he understood Radio 1 was planning to broadcast could be hit.
About 5,000 of the BBC's 27,000-strong workforce are members of Bectu and another 3,500 are in the NUJ. A third union, Amicus, is also taking part.
The unions say "many thousands" of non-members could also walk out in sympathy.
Why is the BBC making the cuts?
Mr Thompson says he is trying to ensure there is still a strong BBC in five, 10 or 15 years time.
Savings are being made to meet targets set by the government in 1999 and convince current politicians the corporation is providing value for money.
It is better that the BBC makes the cuts rather than have an unhappy government come in and do it for them, he argues.
He also wants to make sure the BBC is not left behind in broadcasting developments on the internet, mobile phones, TV, radio - and any other new technology else that may arise.
And some money will go back into programmes. By 2008, £355m a year will be available and priorities include TV drama, comedy, music and "knowledge-building programmes".
Why are the unions objecting so strongly?
The cuts will "rip the heart" out of the BBC, according to the National Union of Journalists (NUJ).
The NUJ has joined forces with the Broadcasting Entertainment Cinematograph and Theatre Union (Bectu) and manufacturing union Amicus for the campaign.
The unions called the strike ballot because the corporation could not rule out some compulsory redundancies - as well as voluntary redundancies and getting rid of staff on short-term contracts.
It was "the worst package of change ever seen at the BBC", the unions said.
"We're not against an efficient, productive, BBC - but many of Thompson's proposals are going to make it worse, not better," Bectu said.
And the NUJ said remaining staff would have to work harder to maintain standards and the figures "simply do not add up".
"They are based on questionable assumptions and fail to take proper regard as to how money could be saved without axing jobs", it said.