This volume contains the complete proceedings of a NATO Advanced Study Institute on various aspects of the reliability of electronic and other systems. The aim of the Insti~ute was to bring together specialists in this subject. An important outcome of this Conference, as many of the delegates have pointed out to me, was complementing theoretical concepts and practical applications in both software and hardware. The reader will find papers on the mathematical background, on reliability problems in establishments where system failure may be hazardous, on reliability assessment in mechanical systems, and also on life cycle cost models and spares allocation. The proceedings contain the texts of all the lectures delivered and also verbatim accounts of panel discussions on subjects chosen from a wide range of important issues. In this introduction I will give a short account of each contribution, stressing what I feel are the most interesting topics introduced by a lecturer or a panel member. To visualise better the extent and structure. of the Institute, I present a tree-like diagram showing the subjects which my co-directors and I would have wished to include in our deliberations (Figures 1 and 2). The names of our lecturers appear underlined under suitable headings. It can be seen that we have managed to cover most of the issues which seemed important to us. VI SYSTEM EFFECTIVENESS _---~-I~--_- Performance Safety Reliability ~intenance ~istic Lethality Hazards Support S.N.R. JARDINE Max. Vel. etc.