The modelling and analysis of Flexible Manufacturing Systems (FMS) has been approached through a variety of methodologies, which diverge considerably in their ability to represent and analyse complex FMS features. This paper broadly classifies the chief approaches, and evaluates them against certain prescriptions. Petri Nets and their extensions score highly on the evaluation criteria. A modelling approach is presented based on Conditional Predicate/Transition Nets (CPrTN), which extend the modelling power of Predicate/Transition Nets. CPrTN provide formal, concise and graphical models, eminently suited for modelling the often complex dynamic interactions in an FMS.