The leather industry creates a large quantity of organic and inorganic waste containing chromium. This research examines stabilization of particulate tannery waste in type II Portland cement. Several clays, Brazilian polycationic smectite modified in laboratory and commercial clays were used as additives with the aim of optimizing chromium adsorption. Tannery waste was added in quantities of 10, 15 and 20% relative to cement mass. The solidification components were analyzed separately and in combination in the solidified mixes using X ray diffraction. The analysis showed that reactions between the waste and the cement occurred, and that the tannery waste modified the final compounds of the system. Calcium sulfate present in the waste increased ettringite formation. Chromium also reacted with cement, since compounds with chromium and calcium were identified. Substitution of aluminum and silicon by chromium was also observed.