The British music industry has secured access to the names of 33 people it suspects of sharing up to 72,000 music files on the internet.
The BPI wants to encourage legal downloading
The British Phonographic Industry (BPI) applied to the High Court for internet service providers to hand over personal details of the alleged file-sharers.
The internet services now have two weeks to hand over the identities.
The BPI is seeking compensation and legal costs from those accused of distributing the music.
"This court order should remind every user of a peer-to-peer filesharing service in Britain that they are not anonymous," BPI general counsel Geoff Taylor said.
"We are continuing to collect evidence every day against people who are still uploading music illegally, despite all the warnings we have given.
"If you want to avoid the risk of court action, stop filesharing and buy music legally."
The BPI has adopted an aggressive stance over file-sharing, targeting those it believes are among the worst offenders.
It has revealed further details of another 31 people involved in a round of legal action in March.
It says about a third of those being chased for compensation were parents of children who were using their accounts to illegally distribute music.
"The risks of allowing children unsupervised access to the internet are well-known," said Mr Taylor.
"To that long list should now be added the very real possibility of legal action if music is uploaded to the internet illegally.
"The safest thing that parents can do is check their computer regularly and disable any file-sharing software."
The UK industry previously took action against 26 file-sharers in October 2004.
Those cases have now been settled, with defendants paying a total of more than £50,000 in compensation.