Since the mid 1980s, a mass of scholarly material has been published on sex offender treatment, particularly relating to cognitive behavioural techniques. Alongside this, there has been a gradual recognition by academics and practitioners in the field of the particular challenges faced by those providing treatment for sexual offenders. As well as having to analyse detailed accounts of sexual violence, sex offender therapists are faced with the responsibility of working with some of the most difficult offenders in the system in terms of their generally poor motivation to change and the serious consequences of their reoffending. As a result, various detrimental impacts have been associated with providing treatment to sexual offenders, including stress, burnout and vicarious traumatisation. This thesis presents the results of interviews conducted with a variety of Prison Service staff working with sex offenders on the Sex Offender Treatment Programme (SOTP), which has been hailed as the ‘largest multi-site, cognitive behavioural treatment programme for sex offenders in the world’. Participants were asked about the positive and negative effects of working with sexual offenders, the quality of training they had received, and what types of personal and organisational support were available to them. The results show that the Prison Service needs to give greater consideration when selecting candidates to deliver the SOTP, and those individuals who have been a victim of sexual abuse should be excluded from the recruitment process. In addition, it is concluded that there should be further staff training for those working on the SOTP, and that existing sources of organisational support need to be improved.