The US music industry has started legal action against more than 500 users accused of sharing hundreds of songs online without copyright.
The music industry blames online piracy for falling sales
It is the largest number of lawsuits filed at one time since the Recording Industry Association of America (RIAA),
launched its campaign last year.
The RIAA, which represents the big record labels, blames file-sharing for a global decline in album sales.
Critics have said the legal action is misguided and ignores market changes.
Music lawyers have filed the latest cases against unnamed defendants who have individual internet addresses and are expected to work through the courts to learn their names and their precise addresses.
"Our campaign against illegal file sharers is not missing
a beat," said Cary Sherman, president of the RIAA .
"The message to illegal file sharers should be as clear as ever."
The RIAA said each person was illegally distributing an average of more than 800 songs online.
More than 1,600 people have been sued by the US music industry since last year.
Each user faces potential fines or settlements
that could cost them thousands of dollars.
Earlier this month the UK music industry said it was considering legal action against Britons who swapped songs online.
The US music industry says its campaign of legal action has caused file-sharing to drop.
However, the number of people illegally downloading copyrighted tracks from the internet has risen after a six-month slump, analysts in the US said earlier this month.
The drop in media coverage of the RIAA's legal action against illegal downloaders may also have contributed to the increase, analysts said.