There are certain formal similarities between the problems of devising policies for economic stabilisation and those of designing automatic control systems in engineering. An automatic control system is made up of a number of interrelated components. The dynamic characteristics of each component can usually be described fairly accurately by a differential equation. The complete control system can therefore be represented by a system of equations or mathematical model. Methods have recently been developed by engineers for analysing the dynamic properties of quite complex models, and procedures have been evolved for finding ways in which a given system may be modified to reduce the fluctuations which occur when it is subjected to external disturbances. These methods and procedures can also be used for the analysis of dynamic process models in economics. There are several good books on the theory of closed-loop control systems, but they are written for engineers, and the technical language and examples used form an almost impenetrable barrier to those who have not had engineering training. Economists will therefore be grateful to Professor Tustin (1954), who is head of the Department of Electrical Engineering in the University of Birmingham, for writing a book on the subject which enables them to avoid these difficulties and for suggesting possible applications of the methods to the study of the problems of economic stabilisation.