Evaluation of regional psychiatric services is essential for effective and economical planning and requires a complete and accurate source of data about individuals in the system. Routinely collected statistics describe only events, and cannot link data about individuals over time. This is possible with record linkage systems (or case registers) which are systematic standardized data collections about individuals' contacts with specified facilities over time. Such data bases have a wide range of clinical, epidemiological and administrative functions. The confidentiality of such systems is of paramount importance and is maintained by several safeguards. There are numerous technical considerations in establishing and operating record linkage systems. A wide variety of studies have been produced from systems around the world. An ongoing collection of linked data is required for many types of research and particularly for service evaluation. In times of cost constraints and diminishing resources, it is essential to deliver psychiatric services in the most effective and cost efficient manner possible.