NFL players will be tested for human growth hormone for the first time this season after a new drug policy was agreed on Friday.
The NFL Players Association (NFLPA) announced new policies had been approved, including testing for HGH.
Among other changes were an independent arbitrator hearing appeals for positive tests, and an increase in the threshold for positive tests for marijuana.
NFLPA president Eric Winston said the agreement was good for players and the league.
"This is an historic moment for our players and our league," he said in a statement.
"We have collectively bargained drug policies that will keep the game clean and safe, but also provide our players with an unprecedented level of fairness and transparency.
"Players should be proud of their union for standing up for what was best for the game."
Included was a change to the punishment for a first-time positive test for amphetamines.
An off-season positive test without a therapeutic use exemption will be considered under substance abuse, while in-season it will stay under the performance-enhancing drug policy.
Players banned for amphetamines during the most recent off-season could have their suspensions lifted as the policy is retroactive.