Lance Armstrong. Alex Rodriguez. Kory Friesen.
Flouting rules for performance-enhancing drugs has felled some of the biggest names in sports. Now that list could include competitive video game players like Mr. Friesen, after he boasted that he, his teammates and other professional gamers took prescription drugs to help them focus in a competition.
In response to those comments, the Electronic Sports League, one of the most successful leagues in competitive video gaming, said on Wednesday that it would test players for performance-enhancing drugs starting at a tournament in August. E.S.L. said it would work with two international agencies — the same ones that help oversee anti-doping policies for cycling, the Olympics and other sports — to create anti-doping guidelines and a testing program for players.
The announcement is perhaps the clearest sign yet that e-sports, as professional gaming is widely known, is evolving into a mainstream form of competitive entertainment. This year, overall revenue from the global e-sports business is expected to surpass $250 million from more than 113 million e-sports fans worldwide, according to estimates from Newzoo, a games research firm.
But the growing stakes for players — prize money is expected to reach $71 million — is creating new temptations.
"We want to create a level playing field for all competitors and maintain the integrity of the sport," said James Lampkin, vice president of professional gaming at E.S.L.
E.S.L. has long had a general prohibition against doping, but its rules did not specify which drugs were not allowed, and the league did not police players. That changed, though, when Mr. Friesen, who plays under the name Semphis, was interviewed earlier this month and said that he had used Adderall during an E.S.L. tournament for the shooter game Counter-Strike while playing with a team called Cloud9.
In the interview, which was posted on YouTube, Mr. Friesen said that his teammates also used the drug, which is prescribed to people with attention deficit hyperactivity disorder but is commonly abused by some to help with focusing.
"We were all on Adderall," Mr. Friesen said of his team, for which he no longer plays. "Tons of people do it."
In an interview on Thursday, Mr. Friesen, 26, said that he used Adderall out of desperation when his team was in the midst of a losing spell.
"It was just one of those things where it's like, maybe it would help," he said in a phone call from his home in Abbotsford, British Columbia.
It did not help. E-sports competitions look a bit like a trading floor, with players yelling directions to their teammates on where to go and who to ambush while simultaneously focusing on their own controllers and screens. Mr. Friesen said concentration drugs could probably help with the shooting bits, while making it harder to absorb directions.
"You don't just take Adderall and instantly become better," he said.
Jack Etienne, Cloud9's owner, said: "We don't agree with Kory's statements about Cloud9, and don't condone the use of Adderall unless it was prescribed for medical reasons. The team is willing to submit themselves to drug tests prior to events if event organizers offer them."
As part of its new anti-doping effort, E.S.L. said it would team up with the National Anti-Doping Agency of Germany to help develop a new policy. The league said it would also meet with the World Anti-Doping Agency about enforcing the policy.
There are unique challenges with testing e-sports players. While traditional athletes perform at live events in the same location, some preliminary e-sports competitions are held online, with players scattered around the country and abroad. No one except a roommate might see one of them popping a pill before an important qualifying round.
Mr. Lampkin said E.S.L. would explore with the anti-doping agencies how well current testing methods detect drug use. He said that the whole industry may have to switch from online competitions to predominately live, in-person games.
"A lot of this is going to affect the nature of the entire industry," he said.
Traditional sports and e-sports have a similar motivation for curbing the use of performance-enhancing drugs: legitimacy. Traditional sports leagues, like Major League Baseball, worry that performance-enhancing drugs can raise doubts about a level playing field. What value is there in sacred home run records, for example, if modern baseball players can get a big boost of strength from a drug?
E-sports leagues and advocates, meanwhile, crave acceptance as a mainstream sport. By turning to some of the top anti-doping agencies, the leagues take a step closer to acting like a traditional sports league — adding to their sellout crowds and million-dollar paydays.
"The more e-sports grows, the more it is going to be sanctioned by a governing body, and it was only a matter of time before this was part of it," said Hector Rodriguez, owner of OpTic Gaming, a professional team. "We're becoming an actual sport, so that's why I welcome it. It's an indication of growth."
Although competitive gaming has been around for more than a decade, it has emerged as a serious business in the last few years. Game publishers like Blizzard Entertainment, Riot Games and Valve, and independent leagues like E.S.L. and Major League Gaming, have invested heavily in producing polished live events that can attract tens of thousands of spectators.
Video streaming services like Twitch have been critical for bringing tournaments to millions more viewers online and creating conduits for players to interact with fans. Big corporate sponsors are also beginning to cater to e-sports fans.
Energy drink makers, in particular, have turned to marketing their products for gamers, suggesting that the caffeine- and sugar-filled beverages can improve play.
Bruce Dugan, a spokesman for Major League Gaming, said that the organization's policies prohibit the use of performance-enhancing drugs. However, the league has never conducted drug tests of its players.
"Now that a lot of attention is being paid, it's something we'll look at for the 2016 season," he said.