This Note presents a few selected results of an experimental testing program carried out at the ESRF in Grenoble, France. X-ray microtomography (with a spatial resolution of 14 μm) has been used to evaluate the onset and evolution of shear banding in a fine-grained stiff soil under deviatoric loading. It allowed detailed observations of strain localization in a specimen during the test, including the presence of more than one shear zone and a varying degree of dilatancy and/or crack opening.