Abstract: This radiography process utilizes dual-energy rays and comprises, in order to differentiate bone, lean and fatty tissues at the same time, an improvement consisting in assessing the total length penetrated by each ray while correcting the errors which may be produced by internal gas pockets. One proceeds as follows: selection of certain rays which have not penetrated bone tissues; calculation of the thicknesses of lean and fatty tissues penetrated by these rays according to the two attenuations, the sum of these two thicknesses being the length of attenuation; estimation of the length of attenuation elsewhere, in particular by means of interpolations; and calculation of the thicknesses of the three categories of tissues penetrated according to this total length of attenuation and the two attenuations.