Constructive solid geometry has been used to estimate the shape and inertia of the human body. Hanavan I used geometric solids to represent each segment of the body and calculated moments of inertia from the dimensions and estimated mass. Jensen improved on the shape representation by increasing the number of geometric solids per segment, with two cm wide elliptical cylinders of given density and major and minor axes measured from orthogonal 35mm photographs of the supine subject. Changes in segment principal moments and other parameters, with age, between 4 and 20 years have been reported for 88 male subjects. The accuracy of this approach for some segments was questioned by Hatze who proposed diverse geometric solids to accommodate the more complex surfaces. A battery of 242 anthropometric measures was used and inertia parameters reported for four subjects. Computerized tomography has also been used to estimate segment shape and inertia. Ackland et al using six scan sites and the leg segment of a 29 year old male and an embalmed 65 year old cadaver, reported that the error associated with the estimation of volume was greater than the error due to the assumption of uniform density. It appears then, that more exact procedures for estimating segment volume may lead to improved estimates of segment inertias. The purpose of this study was to develop a simple technique for determining the surface coordinates at pre-set elevations on an object in order to investigate further the effect of shape representation on segment inertia estimations.