Every British athlete taking part in the Beijing Olympics will be given a drugs test before the games this year.
It's one of the biggest ever crackdowns on drug use, and more than 1,500 tests will be carried out.
The checks will happen without warning, at training camps and big events, and there's no limit on how many times an athlete can be tested.
"We have a duty to show that British teams are drug-free," said UK Sport's director of drug-free sport John Scott.
"We want the British public to have confidence that the performances they are watching are from athletes who have achieved success through four years of hard work, determination and dedication - and not through cheating," he added.