Iodine anion which is contained in water and food stuffs determines the biological activity of the thyroid hormones (thyroxine and thriiodothyronine) which regulate the development, the differentiation and the intensity of the organism’s metabolic processes. Iodine deficiency in water and food products as well as an increasing consume of the tiocianat anion contained in food stuffs, tobacco smoke, formed on nitroprussid metabolization, significantly increase of the iodine deficiency disorders (IDD) risk. It is one of the most spread non-infections deseases characteristic for the population of the planet including Moldova Republic.The model of the IDD in experiments on laboratory animals contributes to the study of definitely pathogen mechanisms rise and the course of this pathological process, gives the possibility for the utilization of the investigation methods, the use of which is impossible in clinic. Besides that the experimental model is an important object for the checking of the therapeutic effectiveness of the pharmacological preparates on this pathology. The aim of this investigation was the study of tiocianat concentration in blood and urine of the laboratory animals after chronic administration. The study was performed on white male rats which weighed between 110-130 g. Tiocianat of potassium was administrated daily. The dose was 10 mg/100 g and 20 mg/100 g b. w. The tiocianat determination in blood and urine was carried out by the colorimetrical method, T4 and T3 were quantified by radioimmunoassay. The tiocianat anion’s concentration in urine and blood correlated with the dose of the administrated preparat (r = + 0,86, r = +0,90). In case of surplus of consumption the tiocianat is excreted by kidney. The intensity of the excretion of tiocianat is directly proportional to the administrated dose. The greatest concentration of tiocianat in urine was detected during 24-48 hours. The complete excretion of tiocianat from blood resulted 120 hours after the stopping of the administration. Tiocianat administration causes some signs, which characterize the hypothyroid state. The decreasing of thyroxine and triiodothyronine in blood correlated with the dose and continuantion of the treatment. 10 days later the frequency of the palpitation rate of the heart diminished 22%, (P < 0,05). After 15-20 days the setback of the body weight increase was detected. After 20 days the horizontal activity in an ”open field” test decreased 30%. It was established that a prolonged tiocianat administration led to disorders in thyroid function and allowed to use this preparation for the model of IDD in chronic experiments.