This paper considers the scope for using Expert System techniques for Strategic Marketing decisions, with particular reference to the question of site location. It draws on a research project currently being undertaken by the authors at University of Wales, College of Cardiff. The basic theme of the paper is that applying Expert System techniques in this area is a difficult challenge due to the lack of an agreed body of formal expertise, and hence that system developers need to be careful to limit their ambitions. The authors suggest that progess can be made by drawing on the knowledge of the end user. The aim should be to build models which like spreadsheets refelt the user's view of the world and permit experimentation with basic assumptions. A further theme is that theoretical models founded on gravitational principles can act as a platform for a rule based system.