Open access. Personality Disorder (PD) is an enduring, multi-faceted mental disorder, associated with adverse health effects, difficulties with interpersonal relationships and in some cases increased risk to others. A limited number of dedicated forensic mental health services are available for serious offenders with severe personality disorder. The recent Offender Personality Disorder (OPD) strategy aims to ensure that most such offenders are treated in prison rather than secure psychiatric services, except in highly complex cases where this is not possible. While the strategy sets out very broad criteria relating to this, greater clarity is needed to support decisions about appropriate transfer and hence enhance public protection. This study explored which characteristics professional experts associate with appropriate transfer from prison to forensic mental health services for high-risk offenders with PD.