Personality changes in frontal lobe disorders are easy to recognize, but their evolution can be hard to predict. Both focal lesions and diffuse neurodegenerative processes may produce personality change based on interruption of prefrontal cortex or subcortical structures that comprise the frontal-subcortical circuits. Observed changes in personality have been classified by behavioral neurologists into three frontal-subcortical circuit syndromes, yet a given patient may defy this classification system by manifesting only selective features of one or more syndromes simultaneously, based on the neuroanatomic distribution of pathology. The orbitofrontal syndrome is the most well known and consists of major antisocial behaviors such as disinhibition, emotional lability, and impulsivity. In some cases, changes are severe enough to lead to new onset of criminality. Apathy and amotivational state lie at the other end of the personality change spectrum. Many psychologic instruments can measure the degree of change in personality, but none of them can be used to extrapolate a patient's ability to function at home or at large in society. The psychopathy checklist by Hare may predict risk of violence but has been validated only for use in criminal populations.