As with previous rounds of suits filed by the music industry group, the "John Doe" lawsuits come without names attached. The identities of the individuals are expected to come out through a court discovery process.
The new round brings the total number of people sued in the United States for trading music online to 3,429, the RIAA said.
"It's as important as ever that we continue to enforce our rights and ensure that fans enjoy digital music in a fashion that supports the creative process rather than one that robs it of its future," Steven Marks, RIAA's general counsel, said in a statement. "The online marketplace has changed dramatically since we began this campaign."
The RIAAagainst file-swapping individuals a year ago this week. The efforts have seen substantial growth in the public perception of file trading as a potentially illegal activity, but the overall effect on music swapping .
The number of users on Kazaa, still the most popular file-swapping network, has declined somewhat over the past year, while showing considerable seasonal fluctuation, according to analysts.
However, the popularity of other online networks--particularly a newer rival called eDonkey--has grown substantially over that time.
Close observers of the networks say file swappers are keenly aware of the lawsuits, however.
"There have been a couple of big impacts from lawsuits," said Marc Morgenstern, CEO of Overpeer, a company that seeds file-swapping networks with fake files in an attempt to protect copyright holders' work. "Many more users are not offering files for upload, while still downloading. Many users are moving to other networks (aside from Kazaa)."
Most of the lawsuits are still going slowly through the court process, as the RIAA seeks to match its digital evidence of copyright infringement to the names and identities of actual Internet subscribers. About 600 cases have been settled so far, a representative for the music industry organization said.
Tuesday's suits were filed in St. Louis, Denver, Washington, D.C., and New Jersey.