Warning: Nearly every one of the compounds on this list is illegal to possess without a doctor’s prescription. Most steroids used by casual bodybuilders are often acquired from underground sources without any verification of the product’s efficacy.

“We have to educate people,” says Thomas O’Connor, aka the “Anabolic Doc,” who specializes in patients seeking recovery from anabolic-steroid use. O’Connor does not advocate the use of any of these drugs and has dozens of horror stories from patients to support his position—including, in extreme cases, death. But he also knows that he cannot stop people from experimenting. And Fakhri Mubarak, a prep coach who speaks openly about his own steroid use, strongly recommends finding a health professional you can work with if you do choose to use performance enhancers.