Introduction The rapid increase in the volume of information used by practicing physicians in the performance of diagnosis and therapy has made it more and more difficult to keep informed of developments in numerous medical fields. As a result it has become necessary for physicians to focus their attention on increasingly narrow areas of knowledge and specialization in order to retain maximum proficiency in practice. Problems involving memory, and correlation and transmission of information by physicians will undoubtedly continue to increase at a rapid rate. These may well cause further specialization of interests. Therefore, communication among physicians working even in closely related fields may be more difficult because of large areas of inefficiently utilized knowledge. The application of large-scale electronic computers for the processing of medical information should prove useful for the differential diagnosis of diseases, the storage and retrieval of medical history data, analysis of medical information, and as