The utility of X-radiography for the study of microcracking in concrete is significantly enhanced by impregnating cracks and voids with a lead-nitrate contrast agent. When an X-ray flux is passed through a polished concrete specimen, X-rays are readily attenuated by the contrast agent in the cracks, which produces a sharp tonal contrast in the resulting radiograph between cracks and surrounding concrete. Radiographs obtained using this technique are compared with more conventional X-ray images of the same specimens. This method is similar in concept to neutron radiography, in which a neutron-attenuating contrast agent is used for enhancing crack images.