BBC Sport takes a look at cycling's premier event, the Tour de France, to see how the competition has been affected by drug cheats since 1998, and whether the issues to hit the sport have improved in recent years.
Where have the drug cheats come from?
Australia - 2
Austria - 1
Canada - 2
Colombia - 1
Denmark - 2
France - 15
Germany - 10
Great Britain - 0
Italy - 11
Kazakhstan - 5
Lithuania - 1
Luxembourg - 4
Netherlands - 3
Russia - 5
Slovenia - 1
Spain - 36
Switzerland - 8
USA - 21
How many drug cheats featured in the Tour?
Seven Italians tested positive while two were sanctioned without a test and one admitted without a test.
Three Spanish, four German, five Swiss and five French cyclists tested positive.
A pair of Australian and Dutch cyclists admitted without a test while two of their compatriots tested positive.
Out of three Americans, including the winner, two tested positive and one admitted without testing.
Out of three Swiss cyclists, one tested positive, one was sanctioned and the other admitted without a test.
One French and one Belgian cyclist were sanctioned without a test, while one Spanish and one Colombian cyclist tested positive.
Five cyclists tested positive including the winner from America, three cyclists from France and one from Belgium.
Two more cyclists from Spain and France were sanctioned without a test.
Five cyclists tested positive including the American winner and three cyclists from Spain while one Dutch cyclist admitted without a test.
Five cyclists tested positive. Two from America, two from Spain and one from Lithuania.
Seven athletes tested positive with two coming from the States, two from Spain, one from Kazakhstan, one from Germany and one from France.
Two more Spanish cyclists were sanctioned without a test while one admitted without a test.
Two cyclists from America tested positive with more failed tests coming from Germany and Belgium.
Four were sanctioned from Spain (two), Italy and Slovenia.
There were six positive tests from America (three), Germany, Kazakhstan and France.
Four were sanctioned from Spain (two), Denmark and Russia.
Three positive tests included the winner from America, France and Spain.
Spain had four doping violations (three positive, one sanctioned) while Kazakhstan (two), Italy and America also failed tests.
Spain, Austria, Luxembourg, Kazakhstan, Slovenia, France and Germany all had at least one failed drugs test.
Two from America and Spain were sanctioned later.
Spain (two), America, Luxembourg and Russia all failed tests while another American was sanctioned later.
The winner from Spain and one Russian cyclist failed a drugs test while one Canadian admitted without testing.
America, Russia and Luxembourg all tested positive while one Spanish cyclist was sanctioned later.
There were two positive tests from Russia and Luxembourg.
Two Spanish cyclists broke anti-doping rules. One failed a drugs test while the other was sanctioned without a test.
One Spanish cyclist was sanctioned without a test.
One Italian cyclist tested positive.