An important aspect of clay paste extrusion is the pressure as a function of extruded velocity/distance traveled. Therefore, the present theory concentrates on deriving basic equations that control the clay paste flow behavior of rectangular extrusion process during the steady-state flow. The main parameters which control the extrusion pressure are the effective stress in compression of the clay paste, the geometry of extrusion tools and billet, operational conditions and the coefficients of friction between the barrel and the die land surfaces. The theoretical extrusion pressure results were analyzed and discussed thoroughly. Finally, it can be concluded that the present theoretical analysis serves to place the present approach in the context of work on other extrudable materials of different geometry. In addition, it can be used as an effective tool for evaluating and obtaining clay paste materials with optimized properties for extrusion process in the ceramic industry. Copyright© 2010 Praise Worthy Prize Srl-All rights reserved.