A case register constitutes a central file to which are reported all persons with a specific diagnosed illness or all contacts with a particular group of medical services over a long period of time. Case registers have proved their usefulness in chronic disease for both administrative and epidemiological purposes. In mental disorder, as in most chronic disorders, the recurrent nature of the illness, the multiplicity of contacts with medical services, and the increasing number and variety of available resources make any investigation complex and particularly susceptible to duplication in counting. A case register, by name matching, can provide an unduplicated count of patients and a record of each individual's longitudinal experience, facilitating the systematic study of the illness or the type of care.1Electronic data processing has now extended the potential of a case register by permitting almost unlimited data storage, by considerably