Britain's anti-doping chief has called for insiders to blow the whistle on sportsmen who they suspect of doping.
Chambers was banned for two years for taking THG
UK Sport's director of drug-free sport, John Scott, said: "There must be knowledge in the system. I'm convinced that people know what's going on.
"We're looking for whistleblowers. I would encourage people to share information that they might have."
The Balco scandal of 2003 was only discovered when a syringe of THG was anonymously sent to the authorities.
British sprinter Dwain Chambers was banned for two years after he was found to have taken THG, a steroid that had been tweaked to make it impossible to detect through existing drugs tests.
Scott said: "A lot of it will come down to people sending substances to laboratories, as we saw with Balco.
"Athletes want to compete against clean athletes."
Scott was speaking as UK Sport announced that it had completed a record number of drugs tests - almost 8,000 - in 2005-6.
But despite that figure - of which 1.5% produced positive tests - UK Sport will be changing the way they target drugs cheats.
A system of "intelligent testing" - with particular attention to out-of-competition testing - is being phased in.
Scott said that dope-testers would be targeting athletes at particular times, rather than just testing per se.
That would include studying when athletes are most likely to be tempted to cheat - for example, in the run-up to a major competition or when coming back from injury.
Scott said: "It's not all about the number of tests - it's about us testing effectively.
"We're trying to understand the motivation of the athletes.
"We need to ensure that each test we carry out is properly targeted at those considered to be in the high-risk category.
"Unfortunately some will do anything to win - but any athlete risks extreme penalties if they dope.
"The systems are better and the testing regime is better."
But he admitted that the next generation of doping threats would be extremely hard to detect.
"Gene doping is ringing a lot of alarm bells," he said.
"The potential for genetic manipulation is there. It is a very scary situation."