Seventy-five former players are suing the NFL, claiming the league intentionally withheld knowledge of the damaging effects of concussions for 90 years.
The plaintiffs claim that "the NFL knew as early as the 1920s 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 players are seeking unspecified damages.
Most players listed their wives as co-plaintiffs. Helmet maker Riddell also is a defendant.
The lawsuit, first reported by TMZ.com, alleges that the NFL did not admit that multiple concussions can affect memory and cause dementia and chronic traumatic encephalopathy (CTE) until 2010.
League spokesman Greg Aiello issued a statement Tuesday saying the NFL has not "seen the complaint but would vigorously contest any claims of this kind."
Riddell spokeswoman Laura Moore said the company had not yet reviewed the complaint and its policy was to not comment on pending litigation.
All of the players named in the suit claim they have suffered injuries due to multiple concussions.
However, the suit claims that an NFL-authorized 1994 study concluded there was "no evidence of worsening injury or chronic cumulative effects" from multiple concussions.
The NFL only warned active players in June 2010 of the risks associated with multiple concussions and Riddell failed to warn active players until about the same time, the suit claims.
The NFL has made numerous adjustments in the battle against concussions in the past year, including altering rules on how, when and where players can be hit. The league also introduced new tests and rules regarding in-game concussions and authorized studies to determine the quality of helmets worn by its players. In February, commissioner Roger Goodell went before Congress to urge legislators from all 50 states to pass youth concussion laws.
Information from The Associated Press contributed to this report.