My understanding- it depends on the steroid. Some of the older stuff, maybe Winistrol (sp?)- or Stanozolol (Ben Johnson's drug), takes a while to get out of the system. And, they're pretty toxic, especially in pill form. Newer drugs are supposed to be less toxic and stay in the system shorter amounts of time (or are undetectable with contemporary tests, like the 'clear' that Bonds used). It comes down to the testers- the stuff that Manny got popped for is used when the person cycles off, so the body can start producing its own testosterone again, since the synthetic source is gone and the body was used to relying on it. If the tester is looking for something like that, it tells them a lot more than if they're just checking for certain anabolics, or certain testosterone levels- which users throw off by taking Chlomid and crap like that- the testosterone won't be way out of wack if they balance it with a female fertility drug. Or something like that.