Persons who commit arson attract a variety of clinical diagnoses, most commonly personality disorder, intellectual impairment, psychotic illness and substance use disorder. This chapter provides an overview of findings from both the investigative and clinical literature on arson. Arson can be can be used for financial gain, but it is also an act of interpersonal violence. Other motives include vandalism, anger, communication, psychosis, extremism (for example, animal liberation groups) or political motives. There are four distinct modes of arson, each with corresponding offender characteristics: adaptive, conservative, integrative, and expressive. In recent years a number of private and publicly funded secure hospitals within the UK have developed and run specific treatment programmes for persons convicted of arson offences. In the absence of recidivism data, an alternative approach to measuring intervention success is offered by recent literature on 'offence paralleling behaviour'.