Antisocial personality disorder (ASPD) is characterized by a pattern of socially irresponsible, exploitative, and guiltless behaviour. ASPD is associated with co-occurring mental health and addictive disorders and medical comorbidity. Rates of natural and unnatural death (suicide, homicide, and accidents) are excessive. ASPD is a predictor of poor treatment response. ASPD begins early in life, usually by age 8 years. Diagnosed as conduct disorder in childhood, the diagnosis converts to ASPD at age 18 if antisocial behaviours have persisted. While chronic and lifelong for most people with ASPD, the disorder tends to improve with advancing age. Earlier onset is associated with a poorer prognosis. Other moderating factors include marriage, employment, early incarceration (or adjudication during childhood), and degree of socialization.