Psychiatric morbidity is high among arsonists compared to those guilty of other serious offences, and the courts are anyway inclined to refer those convicted of arson for psychiatric assessment. There is, however, very little research that informs the assessment of future arson risk and, sometimes, the concepts of recidivism and dangerousness appear to be treated interchangeably. The current study aimed to examine dangerousness in terms of both recidivism and offence severity. The case notes of N=167 adult arsonists referred for forensic psychiatric assessment over a 24-year period were examined for differences between (i) one-time only and multiple firesetters, and (ii) for characteristics of those who had set serious fires causing serious injury, loss of life or extensive damage. Findings largely support those in the literature with repeat arsonists being younger, single and having a number of attributes suggesting childhood disturbance. Personality disorder and previous time in prison were also associated with repeat firesetting. Recidivism was not associated with the setting of serious fires. Very few variables were able to predict whether subjects had set a serious fire although intentional behaviours such as multiple-point firesetting and the use of fuel and accelerants appear to indicate highly dangerous firesetting behaviour. These indicators differ from those previously reported by psychiatrists as most indicative of future dangerousness.