Background: Arson and fire-setting are highly prevalent among patients in secure psychiatric settings but there is an absence of valid and reliable assessment instruments and no evidence of a significant approach to intervention. Aims: To develop a semi-structured interview assessment specifically for fire-setting to augment structured assessments of risk and need. Method: The extant literature was used to frame interview questions relating to the antecedents, behaviour and consequences necessary to formulate a functional analysis. Questions also covered readiness to change, fire-setting self-efficacy, the probability of future fire-setting, barriers to change, and understanding of fire-setting behaviour. The assessment concludes with indications for assessment and a treatment action plan. The inventory was piloted with a sample of women in secure care and was assessed for comprehensibility, reliability and validity. Results: Staff rated the St Andrews Fire and Risk Instrument (SAFARI) as acceptable to patients and easy to administer. SAFARI was found to be comprehensible by over 95% of the general population, to have good acceptance, high internal reliability, substantial test-retest reliability and validity. Conclusions: SAFARI helps to provide a clear explanation of fire-setting in terms of the complex interplay of antecedents and consequences and facilitates the design of an individually tailored treatment programme in sympathy with a cognitive-behavioural approach. Further studies are needed to verify the reliability and validity of SAFARI with male populations and across settings.