The paper will present a review of research in fuzzy logic controllers, starting with the initial motivation for this work and going on to present some further developments. Cement kiln control remains one important area where the approach is now being applied, but other applications are appearing from the many research workers who have contributed to this work since its initial conception. Recent developments have been in the area of Self-Organising Controllers and many results have been obtained in laboratory applications. The paper will overview the current state of research around the world. For the future, it is of interest to go back to the original motivation and view the controller as an Expert System. There are lessons to be learnt both for Expert Systems and we suggest some possibilities for process control applications.