London 2012 will see the biggest anti-doping operation in the history of the Olympic Games.
150 scientists are set to take 6,000 samples between now and the end of the Paralympic Games, covering half of all the competitors.
Every competitor who wins a medal will also be tested.
The anti-doping laboratory is in Harlow, Essex and more than 1,000 people will staff the laboratory, with up to 400 samples tested every day for more than 240 prohibited substances.
Tunde Popoola, the Nigeria Olympic Committee Secretary-General, said: ""I am very confident that everything possible is being done to catch drug cheats at London 2012.