Shape is a fundamental morphological descriptor, one method of its estimation being from digitally processed images. Elliptic Fourier method is an outline-based morphometrics that has some advantages: it does not require either landmarks or previous knowledge about the shape variation of the objects under study; it can visualize the contour of information and reconstruct the original shape; it can be mathematically normalized to size, rotation and starting point of the contour trace; and it can be conducted automatically using computer software. Hence, the variation could be decomposed into several mutually independent quantitative characteristics. In this manner, unacceptable errors based only on human visual judgment of shape, which is frequently deceptive and misled by size factors, can be effectively eliminated. The present study evaluated the shape of equine distal sesamoids ("navicular bone") in 28 feet belonging to "Cavall Pirinenc Català" by means of Elliptic Fourier methods. No allometric relationship (low coefficient of regression) was demonstrated between area and form of the bone. At the same time, different morphological patterns appeared. Shape differences were centred on the proximal ridge, which moved from a crescentic, oval lucency, slightly oval, to a flat contour, and no concave ridge was detected. So breed does not seem to be very prone to suffer from navicular diseases, as some authors have stated that there is an apparent predisposition according to shape of the proximal articular border. These results provide a baseline to further examine shape quantification in sesamoid morphology.