With a photoelastic method, contact pressure patterns between foot and the floor surface were recorded, occasionally for one minute. The aim of this study is to evaluate the development or maturity of postural control. As a clinical model to be tested, Down syndrome characterized by marked muscular hypotonicity was chosen for quantitative analysis. The following results were obtained ;(1) the center of contact pressure is shifted significantly forward in Down syndrome, (2) the position tends to move forward on the left side in both normal and Down syndrome groups, and (3) there was no distinctive laterality of weight loading on either side. Flaccidity of ankle joint movements such as abnormal eversion was indicated by a special parameter, which was obtained for the first time by this method.