Despite huge societal costs associated with firesetting, no standardized therapy has been developed to address this hugely damaging behavior. This study reports the evaluation of the first standardized CBT group designed specifically to target deliberate firesetting in male prisoners (the Firesetting Intervention Programme for Prisoners; FIPP). Fifty-four male prisoners who had set a deliberate fire were referred for FIPP treatment by their prison establishment and psychologically assessed at baseline, immediately post treatment, and three-months post treatment. Prisoners who were treatment eligible yet resided at prison establishments not identified for FIPP treatment were recruited as Treatment as Usual controls and tested at equivalent time-points. Results showed that FIPP participants improved on one of three primary outcomes (i.e., problematic fire interest and associations with fire), and made some improvement on secondary outcomes (i.e., attitudes towards violence and antisocial attitudes) post treatment relative to controls. Most notable gains were made on the primary outcome of fire interest and associations with fire and individuals who gained in this area tended to self-report more serious firesetting behavior. FIPP participants maintained all key improvements at three-month follow up. These outcomes suggest that CBT should be targeted at those holding the most serious firesetting history. deaths, and $1.3 billion USD costs in property damage (Campbell, 2014). These latter property costs represent only a small amount of those incurred since they do not include some of the wider costs associated with firesetting (firefighting, or health costs or costs associated with wildfire damage). In the UK, there were 53,000 deliberately set fires and 451 fire- Over the past two decades, a small number of cognitive behavioral treatment packages (CBT) have been developed for use with mentally disordered firesetters (Hall, 1995; Swaffer, Hagget, & Oxley, 2001;Taylor, Thorne, Robertson, & Avery, 2002;Taylor, Robertson, Thorne, Belshaw, & Watson, 2006). However, these represent uncontrolled 'in house' therapy conducted with very small numbers of participants. In the largest study available (N = 14), Taylor et al. (2002) reported that a 40-session package of group CBT aimed primarily at reducing problematic fire interest and attitudes in patients with a learning disability led to significant improvements on standardized measures of fire interest and attitudes, anger, goal attainment (e.g., understanding of risk), and self esteem. In the absence 6 of any control group, however, the beneficial effect of this group therapy remains largely unclear. To our knowledge, no further firesetting treatment evaluation studies have been published. Furthermore, no treatment evaluation studies in prison settings have ever been reported. The current study aimed to provide the first evaluation of a specialist group therapy trial for male firesetters in a UK prison. The therapy evaluated differs from previous 'in house' therapies...