Medium secure units (MSUs) have developed a range of nursing services for mentally disordered offenders (MDOs) within controlled environments. This paper examines the potential for such nursing services to be offered to the prison service, in order that prisons can provide a level of mental health nursing that equates with the best practice found in the NHS. A number of key reports are reviewed, with examples on how MSUs could help in interventions against self-harm, suicide prevention, forensic nurse therapy and clinical supervision. An account of how nurses in MSUs and prison health care centres could work collaboratively in developing these initiatives is provided. Finally, a brief case report is given on the treatment of one client with post-traumatic stress disorder.