Around 190 hours of TV shows and 310 hours of radio programmes are to be made available for legal downloading to selected individuals across the UK.
Doctor Who became a target for illegal downloads in March
It marks the second stage in the development of the BBC's interactive Media Player (iMP).
The iMP will allow viewers to catch up with programmes up to seven days after they are broadcast, using the internet to download shows to home computers.
Five thousand people will take part in the three-month trial from September.
"iMP could just be the iTunes for the broadcast industry, enabling our audience to access our TV and radio programmes on their terms - anytime, any place, any how," said Ashley Highfield, BBC director of new media and technology.
"We'll see what programmes appeal in this new world and how people search, sort, snack and savour our content in the broadband world."
Rights-cleared feature films and local programming will also be available as part of the trial, which sees the BBC collaborating with Siemens Business Services, BBC Broadcast and Kontiki Inc.
Increasing numbers of people are using the internet to access audio visual material, but Mr Highfield has warned that take-up may stall without the necessary content to attract audiences.