This paper describes finite element simulations of human ribs in lateral impact. The goal of these simulations is to determine the ratio of the lateral stiffness of an adult's thorax to the lateral stiffness of a six year old child's thorax. The stiffness ratio found is then incorporated into a method developed by Mertz [2] to normalize cadaver lateral thoracic impact data. The results of the analysis is a proposed lateral thoracic impact response of the fiftieth percentile six year old child. The paper presents the development of the finite element rib models, discusses their validity, shows how the results are incorporated in Mertz's method, and presents the proposed child thoracic response curves.