UNLABELLED: After 45 years of successful iodine prophylaxis a total of 6324 subject aged 7 to 70 years from East (72.0%), Central (16.2%) and West Slovakia (11.8%) were examined. The thyroid volume (ThV) by ultrasound was examined in a total of 6045 subjects. Serum level of thyrotropin (TSH) was estimated in 1919 (30.3%) and anti-thyroperoxidase antibodies (anti-TPO) in 2589 (40.9%) subjects. Iodine was estimated in 1983 (31.3%) spot urine samples. The median and 75th percentile of ThV were increasing (respectively) from 3.9 and 5.2 ml (10 yr), 8.2 and 10.2 ml (17 yr), 12.4 and 16.3 ml (31-40 yr) up to 14.1 and 19.9 ml (61-70 yr). The frequency of ultrasound hypoechogenicity as an early sign of autoimmune thyroiditis increased from 3.9% (28/709; 10 yr), 16.3% (66/403; 21-40 yr) and 30.3% (205/665; 41-60 yr) up to 51.0% (48/94; 61-70 yr). Positive anti-TPO level as an other sign of autoimmune thyroiditis was found in 1.6% (11/683; 7-13 yr), 7.3% (47/644; 17-30 yr) and 20.4% (257/1262; 31-70 yr). In the adults 19.0% (268/1409) positive anti-TPO were found. Among 1367 adults 6.2% (N = 85) of TSH levels were higher than 4.0 mU/l and 7.5% (N = 103) were lower than 0.2 mU/l. Among 1504 adults a total of 93 (6.1%) of nodules larger than 10 mm in diameter was found (14 in males and 75 in females). In this study the nature of nodules remained unidentified, since all subjects were referred to additional examinations. Malignant nodules were suspected in 3 females with high serum thyroglobulin level and in one additional female with occasionally found very large nodule. The estimation of urinary iodine showed a majority of values in optimal range (> 100-200 microg/l). CONCLUSIONS: Thyroid volume in about 75% examined subjects of all age groups may be considered as relatively small which is apparently due to 45 years of effective iodine prophylaxis. In spite of that the volume of remaining about 25% thyroids were apparently increased which may be presubambly explained by the effect of mainly genetic, but also environmental factors.