COSREEL (Computer System for Recording Events affecting Economically important Livestock) is an animal health recording system which has been designed for the management of cattle, sheep and pigs kept at the ARC Institute for Research on Animal Diseases. Unlike other, numerical, coding systems for the recording of disease, COSREEL has a versatile alpha-numeric coding system which can record diagnosis of disease, local and general symptoms, medical and surgical treatment, vaccination and antiserum therapy, therapeutic management changes and tests with their results. The system is used for recording management, veterinary and milk data, and is a terminal based system using a remote computer. Various lists for action are produced for both herd managers and clinicians including weekly reports of the production and fertility status of individual cows, and lists of cows due for pregnancy diagnosis or infertility investigation. This paper describes the general features of COSREEL, gives examples of the way diagnoses are coded and discusses the future potential of such a system for the development of a central data base for epidemiological analysis.