Cooking extrusion is becoming an essential processing step in a number of food processes. Modeling of extruder performance is the first step towards the ultimate goal of prediction of product properties and quality based on governing extruder characteristics and operation. The purpose of this study was to develop a numerical model of the cooking extrusion process. This involved. many facets of investigation. A 50% added moisture soy flour dough was selected as the material of study. The material properties for this 50% added moisture dough were then determined. The viscosity of this material was found to be both shear and temperature dependent in addition to exhibiting a yield stress. Both thermal conductivity and heat capacity were determined to be constant over the temperature range of investigation. Finally, although it was discovered that a reaction associated with cooking was present in the system, it was determined that it did not occur under the extrusion processes tested which were to be modelled and hence would not have to be accounted for in the model. These material properties were then incorporated in the three-dimensional finite element program, FIDAP, to model the flow of the l 50% added moisture soy flour dough through an extruder and die assembly. These numerical simulations yielded limited results. Only one case out of the multiple conditions which were attempted converged to a viable solution. As more success was found with a two-dimensional model, it is suggested that the problems of convergence could be due to mesh size and discretization of the three dimensional model as well as the difficult power law index of the material. Suggestions as to methods to overcome these problems are included. / Ph. D.