Self-injury is a major clinical problem on the women's wards at Ashworth Hospital. Ashworth Hospital is one of three special hospitals within England and Wales that provides assessment, treatment and rehabilitation for those legally detained patients under the Mental Health Act (1983) who suffer from a mental disorder and require conditions of special security because of their dangerousness. There is extensive literature on the psychological aspects of serf-injury. However, since patients with self-injury present with damage to the body, it is surprising that there is little information on the physical health care and associated resource costs of this behaviour.