The new technique of colour television image analysis has been used to produce seven-colour contour maps of the radiodensity of micro-radiographs of enamel caries. This method permits the detailed measurement of the mineral content of enamel carious lesions to a sensitivity of +/-3% of the level of complete mineralisation. By selection of appropriate aluminium step-wedges, exposed simultaneously with the tooth section, the whole range of mineral content can be assessed.