This research has developed a technique to be used in the study of the relationship of posture to balance. In order to investigate this relationship quantitatively, a model of the body was developed which treats the body as being made up of eleven rigid body segments, each with six degrees of freedom. The input to this model was wholebody kinematic data and force plate data provided by a bilateral Selspot/TRACK data acquisition system. The model was used to quantitatively evaluate "static" posture. The model was extended to permit the estimation of the position, velocity and acceleration of the body center of gravity and of the individual body segment centers of gravity. In this form the model is a useful tool for evaluating postural control, i.e. dynamic posture. With suitable technical modifications this approach should be useful in the study of the coordination of other complex movements such as gait. The accuracy of the system was evaluated using appropriate mechanical model "body segments", and by analysis of the reproducibility of human subject data.