Personality-disordered offenders are difficult individuals to manage, and knowledge about effective treatment is sparse. In the UK, novel forensic psychiatric services were recently established for the treatment of offenders with personality disorder. In this paper we report the clinical and economic findings from a 2-year follow-up of a cohort of service users recruited from these services. Baseline information on developmental, clinical and offending histories was obtained from case records. Case records were checked at 6 and 24 months for new episodes of self-harm, violence, alcohol and substance use, and offending behaviour. Ratings of social functioning and therapeutic alliance were obtained from service users at baseline, 6 and 24 months. Fifty-six percent of service users were still engaged with the services at 24-month follow-up. Service users involved in the greatest number of behavioural incidents had greater impairment in baseline social functioning and lower IQ scores. There was no significant change in either therapeutic alliance or social functioning at 6 or 24 months. The economic analysis showed that although the services were predominantly run by the Health Service, there were considerable economic burdens shared by other service providers. Treatment costs at six-month follow-up were also significantly higher. Implications are discussed.