Research indicates that most domestic terrorist groups include at least three personality types: a paranoid type, an antisocial type, and persons with "inadequate personality disorder." Whereas well-adjusted people develop a basic trust in others and consider the world a safe place in which they can achieve constructive goals and interact with diverse groups and individuals, people with paranoia have an unchanging mindset that the world as it currently exists is a threatening environment that is doing them harm. Leaders of terrorist groups are typically obsessed with the paranoid belief that the world must be changed to reflect their beliefs and conditions for them to feel safe and content. Terrorist leaders are mentally incapable of accepting and living contentedly in a democracy of diverse ethnicities, races, religious beliefs, and a commitment to an open and free society. Another type of terrorist personality is the antisocial person with a history of criminal activity. Such a person is selfish, narcissistic, and resistant to normative moral restraints on his/her behavior. Whereas the paranoid personality tends to be the leader of a terrorist group, the antisocial personality is drawn to the criminal activities of a terrorist group, because it fits his personality disorder. This paper labels him as an “opportunist” within the terrorist group. The terrorists with an Inadequate Personality Disorder respond to charismatic authority figures who assign them a purpose for their lives that makes them feel important. They do what they are told as “followers” in the terrorist group. Counterterrorist strategies should take into account these personality types and their roles in the terrorist group. 12 references