Forty-seven pediatric patients with autoimmune thyroiditis were followed for an average of 5.18+/-2.89 years. The diagnosis was based on a firm goiter and a positive test for antithyroid antibodies. Initially, 23 patients had euthyroidism, 11 overt hypothyroidism, 6 compensated hypothyroidism and 7 with low TSH. All patients had clinical euthyroidism, except two who had overt hypothyroidism. The thyroid function tests, the size of the thyroid gland and the thyroid antibodies were regularly evaluated. After the follow-up, 26 patients had untreated euthyroidism, 12 with overt hypothyroidism received eltroxin for maintenance of euthyroidism, while 4 had compensated hypothyroidism and 5 low TSH levels. All had clinical euthyroid. The thyroid size was reduced in 12 patients (26%) while 4 (9%) had normal-sized gland. The goiter size in 35 patients (74%) remained unchanged. The antithyroglobulin and antimicrosomal antibody titers fluctuated higher in patients with overt hypothyroidism. Eltroxin was given only to those having overt hypothyroidism with diminished goiter size in 8 patients (73%).