Quiet standing posture is organized by supporting, stabilizing, and balancing the body mass against gravity. The center-of-body-mass is controlled in space within a relatively small base of support. Accordingly, ankle and hip mechanisms are used to control the upright posture in an inverted pendulum-like behavior. Body sway is often estimated from center-of-pressure (COP) measures derived from force plate data. Postural control in the anterior-posterior and medial-lateral directions during quiet standing is achieved by separate strategies; therefore, COP measurements should be analyzed in each direction. Various methods of COP analyses including stabilogram diffusion analysis have been developed, but to reveal the mechanism for reorganization of posture against motor or sensory disturbances, the average location to control body sway within the base of support has to be measured. The body schema is determined depending on both the internal and external environments, for example, the loss of sensory monitoring from a unilateral leg moves the center-of-body sway backwards. Compensatory mechanisms, such as an increased role of hip strategy, are used to maintain the anterior-posterior equilibrium. Lower-limb amputees or hemiparetic patients are not able to utilize the affected ankle mechanism and anterior-posterior COP movement is increased under the sound leg more than under the affected leg. The effects of l-dopa or brain stimulation on the postural control in patients with Parkinson's disease have been estimated by COP-based measurement We can identify the clinical outcomes of rehabilitative treatments by analyzing the patient's optimized standing posture.