The IOC has revealed that 4,770 doping tests were conducted in Beijing
The International Olympic Committee will re-test around 500 doping samples from the Beijing Games to check for traces of a new blood-booster drug.
In October it was revealed that nearly 5,000 samples would be analysed.
But the IOC says it will now "primarily target endurance events in cycling, rowing, swimming and athletics".
Around 400 of the blood tests searching specifically for Cera, an advanced version of endurance-enhancing hormone EPO, will occur in Paris and Lausanne.
A further 100 urine samples will be checked for insulin at a World Anti-Doping Agency-accredited laboratory in Cologne.
The German laboratory recently perfected a test for the hormone, which can serve as an anabolic agent to enhance an athlete's performance.
The first results are expected at the end of March.
The original decision to re-test came after French officials detected Cera during re-testing of Tour de France samples.
The new technology unearthed two drug cheats - Germany's Stefan Schumacher, a double stage winner on this year's race, and Italian Leonardo Piepoli.
The original urine tests had raised suspicions but proved inconclusive.
IOC president Jacques Rogge said after the announcement in October that he hoped the re-testing would work "as a strong deterrent and make athletes think twice before cheating".
It was also a move hailed by several of Britain's top stars in Beijing.
Triple gold medallist Chris Hoy described it as "fantastic" and 400m champion Christine Ohuruogu said: "It is something that is giving us confidence that they are on the ball".
Samples from the Olympics are frozen and stored for eight years, making them available when new detection methods are devised.
Hoy won three golds in Beijing and has welcomed the re-test measures
Any athletes caught by new tests can be sanctioned and stripped of their results and medals.
The IOC says it conducted 4,770 doping tests during the Beijing Olympics, including nearly 1,000 blood screenings.
The IOC disqualified six athletes for doping at Beijing - Ukrainian heptathlete Lyudmila Blonska, Ukrainian weightlifter Igor Razoronov, Greek hurdler Fani Halkia, North Korean shooter Kim Jong Su, Spanish cyclist Isabel Moreno and Vietnamese gymnast Thi Ngan Thuong Do.
Three other cases are still pending concerning Belarusian hammer throwers Vadim Devyatovskiy and Ivan Tsikhan and Polish canoeist Adam Seroczynski.