This paper looks at the process of setting up a Head Injury Register whose aims are: (1) to identify reliably and rapidly patients who have sustained a head injury so that service can be offered to them; and (2) to obtain epidemiological data to identify needs and inform future service planning and development. The register records all cases of head injury in patients aged 16-65, regardless of severity, which present to hospital services in Oxfordshire whether or not admitted as inpatients. It was set up as part of a research project into the value of providing an early follow-up service for head injury patients. The paper highlights the difficulty of identifying these patients reliably. It details the administrative and technological problems encountered, together with some of their solutions.