Athletics has been shaken by the doping allegations contained in the World Anti-Doping Association's (Wada) independent report - but who is involved and what might it mean for the future of athletics?
What are the key findings?
- Russia is alleged to have 'sabotaged' London 2012 through systemic doping: Many of Russia's athletes at London 2012 had suspicious doping profiles, including 800m champion Mariya Savinova.
- Some athletes are alleged to have refused and avoided tests: Athletes refused to take doping tests, gave incorrect phone numbers to anti-doping officials, paid money to cover up positive tests and returned from doping bans early.
- Some doctors, coaches and lab staff were in on the alleged cover-up: Doctors and coaches provided banned substances to athletes, coaches and team officials hindered and bullied anti-doping officials, and laboratory personnel destroyed samples and covered up positive tests.
- And so too was the Russian government: The Russian security service FSB allegedly operated a "culture of intimidation" at the anti-doping labs, and it was "inconceivable" that Russian Sports Minister Vitaly Mutko did not know what was going on.
- The IAAF was 'inexplicably lax' in tackling the problem: Athletics' global governing body the International Association of Athletics Federations failed to deal with the problem until it was too late, delaying its investigation of individual cases so long that suspect athletes were allowed to compete in London.
- Wada needs more money: The World Anti-Doping Agency's budget of $30m (£20m) a year is too small for it to be effective. It needs more investigators and more resources to increase its educational efforts.
- Other countries could be cheating too: Report co-author Dick Pound said the revelations surrounding Russia were "just the tip of the iceberg". He alleged that Kenya "has a real problem with doping and has been very slow to acknowledge it".
- Russia could be suspended from the 2016 Olympics: That is the recommendation of the Wada report, if Russia does not "volunteer to take remedial work". IAAF president Lord Coe says the governing body will wait for Russia's response before deciding on a sanction on Friday.
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What is the evidence?
The report was commissioned to investigate revelations in a documentary by German broadcaster ARD last year that alleged widespread doping in Russian athletics.
It looked at claims made in that programme by whistleblowers from inside the Russian system, including former Russian Anti-Doping Agency (Rusada) official Vitaly Stepanov and his wife Yulia (nee Rusanova), formerly an 800m runner who was banned for doping.
There was also testimony from Russian athletes, including former London Marathon winner Liliya Shobukhova, who admitted to taking drugs and observing corruption.
It also found evidence of destruction of samples, interference with doping controls, and payment of bribes to conceal positive tests.
Medicine and syringes were found in athletes' rooms at a training camp. The report noted that such was the atmosphere of intimidation, many of its interviewees were afraid to testify for fear of reprisals.
What is Russia's response?
It has been mixed. The Kremlin has described the accusations as "groundless". The All-Russian Athletics Federation (Araf) said past problems with doping had been tackled and accused Wada of avoiding established protocols for dealing with doping.
The Araf general secretary Mikhail Butov told BBC Newsnight that they were working to "change the mentality of coaches" but that any ban would punish their "clean athletes".
Sports Minister Vitaly Mutko has said that thousands of samples were destroyed, but says Russia only did so at Wada's request. Domestically, Russian officials have been painting the report as a "politically motivated hit-job".
However, a statement from the sports ministry said Russia was "fully committed to the fight against doping in sport" and would be prepared to co-operate more closely in order "to perfect its anti-doping system".
And Russian President Vladimir Putin has demanded "professional co-operation" with anti-doping bodies after ordering an investigation into the claims.
"The battle must be open," said Putin. "A sporting contest is only interesting when it is honest."
Have athletes been named?
Wada's report recommended that five athletes and five coaches should be given lifetime bans for alleged doping violations.
These allegations are unproven and the athletes (named below) are yet to respond to the report's findings.
The athletes listed below were mentioned in the ARD documentary in December 2014 but the commission says a number of others should also be investigated.
- Mariya Savinova - 800m champion at London 2012 and gold medal winner in 800m at the World Championships 2011
- Ekaterina Poistogova - 800m bronze medallist at London 2012
- Anastasiya Bazdyreva - 400m and 800m runner. Recent winner at Russian Championships
- Kristina Ugarova - Currently ranked 110 in the world in the 1500m
- Tatyana Myazina - 800m runner
Is Russia alone in systematic doping?
Pound's views that these revelations were just the tip of the iceberg were echoed by UK Athletics chairman Ed Warner, who suggested there are "four, five or six nations that athletics really has a problem with".
Yet the implications of the report may also not be limited to athletics alone, with Pound adding it is "not the only sport with a doping problem."
Baseball and cycling have also been beset by doping scandals in recent times, while a corruption crisis still engulfs world football's governing body Fifa.
What happens next?
IAAF president Lord Coe has asked Russia for a response to the report by Friday, when a council will convene to decide the next step.
A potential sanction could be the suspension of Russia if such a proposal receives a majority vote, and it could mean Russian athletes are banned from next year's Olympic Games in Rio.
Russia is a global sporting power, having hosted the 2014 Sochi Winter Olympics and is due to host the 2018 Fifa World Cup.
The report could also have implications for Russia's right to host such events, with UK Athletics chief Warner calling for the country to be stripped of next year's IAAF World Junior Championships in Kazan.
What do the athletes say?
Britain's Goldie Sayers finished fourth in the javelin at the Beijing Olympics in 2008.
She told BBC Sport the situation had left her "frustrated".
"I'm incredibly saddened and devastated for the sport," Sayers said. "When (athletes) train very hard, to think you've been denied those medals is devastating. Not only professionally but emotionally and financially.
"For most athletes it is the thought that you've lost those moments you'll never get back. That is the hardest pill to swallow."