The National Union of Journalists (NUJ) and two other unions representing technical workers were striking to protest against plans by BBC Director General Mark Thompson to cut about 20% of its workforce, or about 4000 jobs.
BBC News 24 and BBC World Service were running large blocks of pre-recorded programming on Monday morning. Its flagship Today radio news programme has been cancelled.
BBC One's Breakfast television programme was running with a basic service and one presenter, and some regional radio programmes were presented by managers. Staff for the foreign language service of the World Service also joined the picket line, the NUJ said.
The BBC said it regretted the strike action and would do everything it could to produce the best possible service.
"Industrial action will not remove the need for further consultation or the need for the BBC to implement changes, which will enable us to put more money into improved programmes and services," it said in a statement.
The NUJ General Secretary Jeremy Dear called on the BBC to "understand and respond to the anger and concern at job cuts, which will undermine quality, threaten the working conditions of staff and devalue the BBC for viewers and listeners".
The NUJ, along with the Bectu and Amicus unions, voted on 12 May to authorise four strike days: 24 hours on 23 May, 48 hours over 31 May and 1 June , and a fourth day without a set date.
They chose to avoid big events such as the Wimbledon tennis tournament, televised on the BBC.
The unions had said they would call off the strike if the BBC granted a 90-day moratorium to the planned staff cuts, guaranteed that any redundancies be voluntary and protected conditions of jobs set to be outsourced.