System Dynamics as a subject has been with us for, suprisingly enough, nearly 30 years. This is, therefore, a suitable point at which to take some kind of look into the future and, since I believe that the future is modified by the past, it is necessary to start with a brief survey of the history. Unfortunately, in a brief chapter it will be necessary for me to generalise much more freely than I would really wish. I hope I may be forgiven if I omit one or two important developments and do less than justice to others.