The International Rugby Board says it is launching its biggest ever Rugby World Cup drugs testing regime at this year's tournament.
More than 300 tests will be carried out over the 44 days of the event and players can be targeted at any time.
Blood testing will be used more than ever before in a bid ensure the detection of human growth hormone, which builds muscle and aids recovery, while urine testing will still be used.
IRB anti-doping manager Tim Ricketts says the ability to detect and mask drugs is changing all the time and the board has to keep up.
The executive director of the International Rugby Players Association, Rob Nicholl, is wary of the crackdown.
Mr Nicholl says the IRB is focusing too much on mistakes players make with supplements or medicine, and too often penalises players for not following rigid testing rules when it should be hunting out the real drug cheats.