This paper addresses the prediction of engineering properties of pultruded structural shapes (e.g., EXTREN(TM), PULTREX(TM)) based on the processing description used by the pultrusion industry. Since the strength-to-stiffness ratio of composites is much larger than that of steel or concrete, deflections are of major concern to the structural designer. In this paper, it is shown how to predict axial, bending, and shear stiffnesses of the structural shapes based on the fiber and resin properties and their arrangement in the cross section. Correlations between properties predicted by this method and measured by full size testing of commercially available structural shapes (PULTREX(TM)) are shown. Intermediate steps in the analysis by comparison to material testing data from samples of the same pultruded section were validated. This work also serves as the basis for more complex analysis of the behavior of pultruded structural shapes that are addressed in companion papers. Recommendations as to how the pultrusion industry may use this model to optimize the performance of new structural shapes are presented.