One in five professional rugby union players in England suffered concussion during the 2018-19 season, according to the latest medical figures released by the Rugby Football Union (RFU).
In 2018-19, 20.4% of players sustained at least one match concussion.
It is an increase from 16% in the 2017-18 season.
The report analysed 407 games and 763 players from 12 Premiership clubs.
For the eighth consecutive season, concussion was the most commonly reported match injury.
In total, there were 166 match concussions and 38 training concussions.
The frequency of concussions - measured by the number of incidents per 1000 hours of playing time - is the second highest it has ever been. The highest recorded concussion incidence was 20.9 per 1000 hours in 2016-17.
The report said medical staff were able to identify more head injuries in 2018-19 following the introduction of a real-time pitch-side video system in the Premiership.
"Improving the detection of these complex injuries to ensure safe removal of concussed players remains a priority, as is developing and evaluating strategies to reduce concussion incidence," it said.
The Rugby Football Union and Premiership Rugby recommends seeking specialist neurological opinion following a second diagnosed concussion during a 12-month period.
England's World Cup winner Steve Thompson is among the players who have started a legal process against English and Welsh rugby union authorities and World Rugby, saying the sport has left them with permanent brain damage.
They have all been diagnosed with the early signs of dementia and say repeated blows to the head are to blame.
Global governing body World Rugby and the Rugby Football Union (RFU) say they take "player safety very seriously". The Welsh Rugby Union (WRU) say it "supported and endorsed the World Rugby comment on the subject".