Horses that try to kick people are extremely dangerous. A kick can occur so quickly that a handler does not see it coming at all. A severe kick can be fatal. Generally, otherwise gentle horses might kick at people out of surprise, fear, when in pain, for self-preservation. Wild horses that have not been handled naturally kick when cornered.

Horses with training problems may habitually kick out of aggression, or to bluff handlers. Horses are taught this behavior in the same way they are taught to engage in many other unwanted behaviors. They perceive it to be easier and more rewarding than alternative (desirable) behaviors. "Cow-kicking" is kicking out to the side or forward and is a somewhat different behavior.

Numerous physical problems, usually involving pain, could cause a horse to kick at people. Your vet can help you determine whether this behavior is a result of physical pain or another disorder. If a physical cause is ruled out, look to yourself, your own handling technique, and others who have handled your horse as both the cause of the problem and the solution.