This publication is sponsored by the American Association for Medical Systems and Informatics. The Board of AAMSI and the Board of the Society for Computer Medicine, one of AAMSI's predecessors, agreed that a book on application of medical systems and informatics for the practitioner would help promote high quality health care and they charged the Committee on Standards of the Society for Computer Medicine to write such a text. It is intended as a guide for the field of medical systems and informatics with emphasis on standards, terminology, and coding systems. The text, a result of three years of research and effort, has been reviewed by the Board of Directors of AAMSI and approved by the Publications Committee. We believe that you will find it valuable and hope to revise it from time to time to meet current needs. On behalf of the members of the Association, we congratulate the authors and thank them for their efforts. WILLIAM A. BAUMAN, M.D. President American Association for Medical Systems and Informatics Preface This book has been written by the members of the Committee on Standards of the Society for Computer Medicine. We have drawn upon the Society's expertise to prepare an easy-to-read and understandable How-to Do-It text for use by those physicians who are considering computerization of their office in one manner or another."