A study of 3 cases of acute bismuth encephalopathy by C. T. scanner revealed indisputable evidence of abnormal hyperdensity in certain brain regions. These hyperdensities, or rather hyperattenuations, are very typical in case no. 1, where the central grey nuclei, especially the caudate nuclei and cerebral cortex, have an important hyperdence appearance. The images are heterogenous, sometimes granular, and are not modified by the injection of a contrast medium. There are also ventricular and cisternal dilatations which are even more remarkable when the age of the patients (less than 45 years) is considered. Cases Nos. 2 and 3 showed hyperdensity which was mainly in the cortical hemispheres. Blood bismuth levels vary according to the date of bismuth stoppage, lying between 850 and 1.350 microgram p. 1.000 ml. The pathogenesis of these tomodensitometric images are discussed as a function the of atomic number of bismuth metal and its unequal distribution in the cerebral parenchyma and the meninges.