The most commonly used AAS in medicine are testosterone and its various esters (but most commonly testosterone undecanoate , testosterone enanthate , testosterone cypionate , and testosterone propionate ),  nandrolone esters (most commonly nandrolone decanoate and nandrolone phenylpropionate ), stanozolol , and metandienone (methandrostenolone).  Others also available and used commonly but to a lesser extent include methyltestosterone , oxandrolone , mesterolone , and oxymetholone , as well as drostanolone propionate , metenolone (methylandrostenolone), and fluoxymesterone .  Dihydrotestosterone (DHT; androstanolone, stanolone) and its esters are also notable, although they are not widely used in medicine.  Boldenone undecylenate and trenbolone acetate are used in veterinary medicine . 
@Geoff: so people are “fucken idiots” if they think The Rock used steroids? I’m terribly sorry to be the one to give you this reality check, Geoff, but you’re in dire need of it, so here goes; I’ve been doing bodybuilding for more than 15 years and I can tell you from my own experience that a lot of the stuff that you see on “natural” stages is often not natural at all – you should really get a grip on reality. Sadly enough, quite a lot of the “natural” guys (I wouldn’t say the majority) do a cycle during the off season and try not to test positive during the competitions (which has gone wrong on more than one occasion). I don’t have a problem with people using non-natural bodybuilding regimes, not at all, but don’t take part in natural competitions if you do, that’s all; go for the non-natural competitions or simply don’t compete. Furthermore, most of the “natural” bodybuilders are not bigger than the Rock; they might be more cut, true, and you might confuse this with “being big,” but most of them are definitely not bigger, volume- and mass-wise. And as far as the Rock’s steroid’s usage is concerned: he apparently admitted to this himself (which, again, is not a “bad thing” in my opinion; to each his own, after all), just check (for example) http:///articles/140046-dwayne-the-rock-johnson-says-he-used-steriods-is-it-just-his-era-that-used .