The influence of an enhanced bromide intake on the uptake of 131-I by the thyroid and various organs and tissues of rats, on the magnitude of the whole-body biological half-life of iodine, and on the body weight and prosperity of rats was followed with the help of radionuclide tracer techniques. Based on the results obtained, we conclude that a high level of bromide in the organism can obviously influence the iodine metabolism in two parallel ways: by a competitive inhibition of iodide accumulation in the thyroid, and by accelerating the iodine excretion by the kidney.