In reply to TimS: True, but how do you distinguish between a training supplement and a (banned) performance enhancing drug? I know creatine is naturally produced in our bodies, but then so is testosterone etc. If I was being cynical, I'd say that creatine isn't banned yet because the IAAF is still working on a test that'll enable effective prosecution!
I'm not into all the ethical arguments about whether it's right or not, but creatine helps your body develop quicker, get stronger, faster and more efficient. It is, therefore, a performance enhancing drug.
If you eat lots of red meat, then the creatine is naturally occuring, but shovelling the stuff in as a liquid or powder is not natural.