Whenever a spaniel of any type exhibits bad behavior, especially toward their owner, the term “Spaniel Rage” gets thrown around. Also known as “Malignant Behavior” this is a form of canine mental illness that is characterized by extremely violent and unprovoked fits of anger. In reality, this is a very rare, violent form of behavior that becomes a diagnosis of exclusion. Most of these dogs have been diagnosed with another form of aggression, including dominance aggression, fear-related aggression, resource guarding, and territorial behaviors. Dominance aggression was the most common diagnosis, when current diagnostic criteria were applied. Many canine behaviorist would like to see the term “Spaniel Rage” removed from the vocabulary.