This book is a collection of invited contributions, each reflec- ting an area of medicine in which computing techniques have been successfully applied; but why the title? From a control system point of view the aim of clinical medicine is to recognise the deviation of a patient from the space of normality, and to propel and steer the patient along a trajectory back to that space. Acquiring and main- taining the knowledge and skills of this process is the function of medicine. The first chapter expands on this view. Subsequent chapters written by experts in their respective areas cover a fair range of application. All give considerable insight as to the ways in which the control system approach, facilitated by computational tools, can be of value when applied to clinical problems. The idea for this book arose naturally out of a symposium held at the University of Sussex, Brighton, England, on "Control System Concepts and Approaches in Clinical Medicine" in April, 1982, spon- sored by the Institute of Measurement and Control and co-sponsored by the Institution of Electrical Engineers and the Royal Society of Medicine. It is not, however, a "proceedings" of this meeting but rather a collection of essays that reflect developing areas in which many have particular interest. We think the volume is timely and hope that the work described will be an encouragement for others.