The Canadian was sensationally stripped of his Olympic gold medal and world record in the 100 metres at the 1988 Seoul Games after testing positive for steroids. After a two-year suspension, he received a lifetime ban in 1993 for a second positive doping test.
Now he is promoting an anti-doping campaign, Pure Sport, which has been launched by a sportswear company.
"Winning a gold medal and being the best in the world it cost me my reputation, my life," Johnson said Thursday in London. "I'm here to try and change that. I'm trying to clear the air and clear my part of life, trying to help future generations and future athletes, athletes of my calibre, who have tested positive, been in the same boat as me, trying to help them and say 'you're not alone.'"
Johnson said he hoped to convince future athletes not to resort to drugs.
"If I can help change the mind of athletes in generations to come, that's what we are here for," he said.
The campaign's backers said in a statement that Johnson will ask sports fans to sign a petition demanding action to "improve the waning credibility of world sport," while demanding a truth-and-reconciliation process across sport.
Johnson will take his message to the Olympic Stadium in Seoul on Sept. 24 — the 25th anniversary of the race where his reputation was shattered.