Aggression in dogs poses a problem for both the owner as well as people in public. A dog that is aggressive may still be a good guard dog or family pet if it is obedient and controllable and is not dangerous to others, but a dog that is excessively aggressive will be a problem to other people, the owner and family, or towards other pets or animals.

Most dog breeds will exhibit one of the four basic forms of aggression to some degree, such as prey instinct, territorial, protection and self preservation. Some breeds were developed specifically enhance their ability to hunt, enhancing the prey instinct, and are aggressive only towards certain targets and not everything.

Other types of aggression include dominance, possessiveness, fear and aggression during mating, which are all expected types of aggression that will usually be corrected with obedience training and socialization.

Excessive aggression is inappropriate aggression that does not lessen with training and socliazation and can sometimes be neurological or caused by a chemical imbalance in the brain. This type of aggression can also be the result of or brain injury and trauma and is very often a sign abusive treatment.

Excessive aggression is not limited to breed in the event of neurological trauma, injuries or disease, but some breeds have a higher rate of excessive aggression from issues that are not disease related. Often the aggression is not due to the breed but the irresponsible actions of the owners and breeders.

Occasionally, excessive aggression can be treated with intensive positive training with a behaviourist or alternatively drug therapies. However it is the responsibility of the owner to keep the dog secured until fully trained.