A photogrammetric measuring device has been under development for automating the detection of variations in back surface shape, in order to discern improvements or deterioration in scoliotic patient conditions, for comparing one patient with another patient, or to collect statistical data on the condition. The system is designed to take into account as carefully as possible the requirements of the medical practitioner as the end-user of the results, especially by providing output that can be exploited. Careful consideration has been paid to clinical requirements, not only in terms of cost and accuracy, but also in terms of convenience to clinical staff and the patient. In this way, the instrumentation is designed to surmount apparent difficulties in having photogrammetric instrumentation accepted into routine clinical use. The surface measurement follows the widely-accepted photogrammetric configuration of a pair of stereoscopic digital cameras, with a projected light pattern to provide texturisation on the human body. It is intended to require no handling by a medical practitioner. The detection of features in the pattern, the determination of stereoscopic correspondence and the formation of the surface model, are carried out in an automated manner. The two images are collected within 0.1 seconds of each other. Although computations are not instantaneous, the current system operates in accordance with requirements, obtaining from 500 to 1000 points to define the back surface to an accuracy of about 1 mm. In addition, the hardware is currently being linked to software which enables one measured back surface to be compared with another by least squares matching methods, to detect differences between the two back shape surfaces. This component is seen as crucial for the acceptance of the instrument by medical specialists.