An expert system called GMX: The Gasket Material Selection Expert was presented at the 1989 SAE Conference(1).* The capabilities of this program have since been increased tremendously by the development of a Mathematical Model which predicts physical flange distortion and gasket compression values for any bolted, gasketed flange configuration. The expert system contains the logic (Rules) and facts (Databases) needed to compare gasket material properties to application-specific requirements and to specify gasket materials that will perform best in the application. The Flange Distortion Model is used by the expert system to calculate certain quantities that are needed to compare materials for the application. This paper describes how material properties and gasket engineering are used to make a material recommendation, and how an expert system and mathematical model have been utilized to make this expertise available to the gasket specifiers.