The aim of this chapter is to provide an understanding of the biological characteristics of psychopathy. It is important to note early on in this chapter that there is no single biological cause of psychopathy, just like there is no single psychopathy gene. Instead, evidence from neuroscientists and biological psychologists show that psychopathy is related to a variety of biological vulnerabilities. This should not come as a surprise as the construct of psychopathy is made up of many similar and different symptoms, which is why psychopathy has become best understood by studying the dimensional construct to help delineate what specific psychopathic traits are related to. For instance, the Interpersonal-Affective (factor 1) features of psychopathy are typically related to low arousal and hypoactivity in the brain, yet Impulsive-Antisocial features (factor 2) are more often related to heightened physiological arousal and hyperactivity in the brain. Again, this should not come unexpectedly because the symptoms of factor 1 and factor 2 are different.