This seems accurate and advisable reading for those who argue people doping should have had more positive drug tests at the time:
Firstly, and most obviously, there was no test for EPO until 2000 at the earliest, and the test could only detect very recent (less than 8 hours) doping.
Secondly, after EPO could be detected, the dopers moved to "blood doping", which is being transfused with your own blood during competition to increase red blood cells (and so improve oxygen transfer to cells).
Thirdly, they also used testosterone, which was difficult to detect because it occurs naturally in the body. A positive result to growth hormones was even blamed on a steak by another elite cyclist!
Fourthly, Armstrong tested positive to cortisone at least once, but a back-dated prescription for a skin cream was used to contest the lab result.
Fifthly, dopers also used to avoid the testers, even lying low in their own houses until the testers stopped knocking on the front door!