Endemic goiter is one of the most important health problems in Turkey. However, there are not enough studies associated with iodine and selenium status. This study was carried out to establish the effects of iodine and selenium levels on thyroid gland size and thyroid functions in 73 healthy school-children, 7-12 years old (mean 9.56 +/- 1.77 years), 38 girls (52%) and 35 boys (48%), living in an endemic goiter area. Goiter was found in 32 of the children (43.8%) by palpation, and 56 of the children (76.7%) by ultrasonography. Mean serum T-3 and TSH levels were in the upper limit of normal, and mean serum T-4 levels were within the normal limits, but mean serum thyroglobulin levels were higher than the normal limits. Mean serum selenium level was 30.84 +/- 23.04 mug/l, and mean urinary iodine level was 3.91 +/- 3.77 mug/dl, appropriate for moderate iodine and selenium deficiency. Thyroid volumes of the children were negatively correlated with serum selenium levels, but there was no correlation with urinary iodine levels and thyroid hormones. In conclusion, school-children in this area had significant goiter problems, probably due to the iodine and selenium deficiencies.