Iodine prophylaxis was introduced in Poland in 1935. It was interrupted twice, the first time between 1939 and 1947 (due to the Second World War and its aftermath), and then between 1980 and 1986, due to the economical crisis in Poland at that time. A voluntary model of iodine prophylaxis (20 +/- 10 mg/kg of household salt) introduced in Poland in 1986, was followed by a mandatory model, implemented at the beginning of 1997, with 30 +/- 10 mg/kg of household salt. In the early sixties, in our Department of Endocrinology 24-hour iodine uptake test was introduced as a routine procedure for evaluating the thyroid gland. The reference value of this test increased in 1986 after discontinuation of iodine prophylaxis, and decreased in 1998, two years after re-implementation of the mandatory model of iodine prophylaxis. In 167 patients (147 with endemic goiter and 20 with no thyroid disturbances) examined between 1998 and 2000 the mean value of 24-hour iodine uptake was 27.3 +/- 10.4%, as compared to the mean value of 45,7 +/- 6.6 % in 1986. In patients with thyrotoxicosis the mean value of iodine uptake was 41.9% +/- 16.2 in 1999 (no.=614), 42.4% +/- 16.9 in 2000 (no.=644) and 37,7% +/- 17.2 at the beginning of 2001 (no.=328). The mean value of iodine uptake in patients with thyrotoxicosis before implementation of iodine prophylaxis was over 60%. The 24-hour thyroid radioiodine uptake test proved to be a useful indicator of changes of iodine intake in a iodine-deficient population. The data presented in this study confirm the importance and efficacy of the iodine prophylaxis introduced in Poland.