According to TMZ.com 75 players have filed suit against the NFL for hiding the dangers of repetitive head trauma, specifically concussions;

According to the lawsuit, filed today in L.A. County Superior Court and obtained by TMZ, the players and their wives claim, “The NFL knew as early as the 1920’s of the harmful effects on a player’s brain of concussions; however, until June of 2010 they concealed these facts from coaches, trainers, players and the public.”

The centerpiece of the argument is the now infamous study published in 2004;

The suit claims the NFL commissioned a study in 1994, titled “NFL Committee on MIld Traumatic Brain Injury” and published a report in 2004, concluding there was “no evidence of worsening injury or chronic cumulative effects” from multiple concussions.

The NFL has posted a quick blurb on their website with the story as well, and NFL Spokesman Greg Aiello had this to say;

“We have not seen the complaint but would vigorously contest any claims of this kind,” Aiello told ProFootballTalk.com.