REUTERS - Factbox on sprinters who have been involved in doping scandals in the past 25 years:
Ben Johnson (Canada). Stripped of his 100 metres gold medal at the 1988 Seoul Olympics after testing positive for banned steroids. Still the biggest scandal to hit the Olympic Games.
Katerina Thanou/Kostas Kenteris (Greece). Thanou (100 metres silver medallist in Sydney) and her Greek team mate Kenteris (Sydney 200 metres champion) were accused of faking a motorcycle crash just before the 2004 Athens Olympics to skip a dope test. They were later given two-year bans.
Katrin Krabbe (Germany). Double sprint champion at the 1991 world championships in Tokyo who never competed at an Olympics after a ban for the anabolic agent clenbuterol.
Linford Christie (Britain). At 32, the oldest man to win the Olympic 100 metres title with victory in Barcelona in 1992. Seven years later, in semi-retirement, tested positive for the steroid nandrolone.
Dennis Mitchell (U.S.). The American, who won gold as part of the U.S. 4x100 metres relay team at the 1992 Barcelona Olympics, was banned for two years in 1998 for excessive levels of the male sex hormone testosterone.
Merlene Ottey (Slovenia). Jamaican-born sprinter who won world 200 titles but was banned from the 1999 Seville world athletics championships after a positive test for nandrolone. Later cleared by the International Association of Athletics Federations (IAAF).
Dwain Chambers (Britain). Finished fourth in the 100 final at the 2000 Sydney Olympics but was banned for two years in 2003 after testing positive for the designer steroid THG in the BALCO laboratory scandal.
Tim Montgomery (U.S.). Also implicated in the doping scandal that engulfed the San Francisco BALCO laboratory. The American set a 100 metres world record of 9.78 in 2002 but later admitted to doping at the 2000 Sydney Olympics.
Marion Jones (U.S.). Montgomery's partner and the biggest victim of the BALCO scandal, Jones became the first woman to win five track and field medals at a single Olympics at Sydney 2000 After years of denial, she confessed to being a drugs cheat and was jailed for lying to federal investigators.
Kelli White (U.S.). Another BALCO victim who admitted to using a cocktail of drugs after winning the 100-200 double at the 2003 Paris world championships.
Justin Gatlin (U.S.). The American, who won gold in the 100 at the 2004 Athens Olympics, has served two doping bans, including four years for excessive levels of testosterone. He won 100 metres bronze at the 2012 London Olympics and two silvers at this year's world championships.
Veronica Campbell-Brown (Jamaica). Twice Olympic 200 metres champion who is suspended after testing positive for a banned diuretic at a meeting in May this year.
Sherone Simpson (Jamaica). Gold medallist at the 2004 Olympics in Athens and a silver medallist last year in London as part of Jamaica's 4x100 metres relay teams, Simpson tested positive for the banned stimulant oxilophrine at June's Jamaican athletics championships.
Asafa Powell (Jamaica). Held the 100 world record between 2005 and 2008. Tested positive for oxilophrine at the national championships in June.
Tyson Gay (U.S.). Completed a memorable sweep of sprint titles at the 2007 world championships in Osaka when he won the 100 and 200 metres and was part of the triumphant U.S. 4x100 metres relay team. Tested positive for a unidentified substance in an out-of-competition test in May this year.
Kelly-Ann Baptiste (Trinidad & Tobago). A member of Gay's training group and 2011 world 100 metres bronze medallist, she withdrew from August's Moscow world championships on the opening day of competition for a doping violation.
(Compiled by Tom Bartlett; Editing by Alison Wildey)