The results obtained up to now indicate that increased intake of some heavy metals causes disorder of bioelements metabolism leading to their blood and organs decrease and higher elimination via the urine. As to lead and magnesium, our investigations indicated that the reaction is reversible and that increased intake of Mg eliminates Pb via urine. Some other findings suggest similar relations between Mg and certain heavy metals, thus pointing to significant role of Mg in toxicology of heavy metals and announcing a new chapter in the toxicology of metals entitled 'Mg in professional and ecotoxicology'. In this report we present the results of our investigations on the effect of Cd on Mg metabolism. The experiment was performed on rabbits given orally, every day, for 4 weeks 10 mg Cd/kg b.w. as aqueous solution of CdCl2. Magnesium content was determined in blood, urine, soft tissues and bones by the AAS method. Under the experimental conditions, Cd lead to statistically significant decrease of blood Mg (p < 0.001 after day 16) which was associated with increased Mg elimination via urine (p < 0.01). Statistically significant changes were not detected in the tissues, except in the liver where we found enhanced Mg content (p < 0.05), while its level in the muscles decreased (p < 0.01).