This paper presents the results of studies performed within the Applied Project of the Ministry of Health and Social Welfare and of the Committee for Scientific Research: "Studies on Iodine Deficiency in Poland", including the school children in Lódź City and seven voivodships of the Central Poland. According to the results, the analyzed regions can be regarded as areas of goitrous endemia of a moderate degree (the goitre was found in 32.7% of examined population); the same regions can also be classified among the regions of mild iodine deficiency (the mean iodide concentration in urine was 64.0 micrograms/l). The obtained results prove the to-date's iodine prophylaxis to be not entirely efficient in the areas of interest, demanding an effective model of iodine complementation in diet to be designed.