Assessing current sexual interest in men who have committed sexual offence can be somewhat problematic, particularly in relation to those who are serving probation, where disclosing offence-related sexual interest may lead to a serious penalty (eg incarceration). This chapter describes the Current Sexual Interest Measure (CSIM) and how it was used to assess men serving their sentence in the community in Texas, USA; comparing them to two groups of men in custody in the United Kingdom. Those serving their sentence in the UK included a group of men who had been convicted of sexual offences, as well as a group of men convicted of violent offences to provide contrasting data. Both groups of men were participating in therapy in a prison-based therapeutic community and so possible effects on the data are considered. In addition, data were collected from men in a lower-security prison to provide further contrast.