A type of organic compound containing a characteristic arrangement of carbon and hydrogen atoms (cycloalkane rings). Steroids occur naturally in all animals, where they act as signaling molecules and are a component of cell mebranes and . Examples of steroids include the sex hormones testosterone and oestradiol.

Artificial or naturally occuring anabolic steroids are drugs that are used to synthetically enhance bone and muscle development. These drugs are banned from use in all equine sports as they can be performance enhancing and are often considered typical 'doping' drugs. 

Steriod based anti-inflammatory drugs (e.g. dexamethasone) are used for a variety of medical indications including pain relief and immuno-supression. These drugs have therapeutic use in horses but are prohibited during competitive use of a horse.