The thyroid gland is most influential large endocrine organ to the body growth and development of skeletalsystem, yet the etiology of thyroid disease is not elucidated clearly. It is reviewed thyroid disease in mostgrowing period in infancy, childhood to preadolescent age under 16 years. Total 84 cases were analyzed in clinicalsymptoms and various thyroid function study and scanning with other laboratory studies at Radioisotope section ofRadiogy and Nuclear Medicine department of Yonsei University Severance Hospital from June, 1975 to August, 1976.1. Among 84 cases, 45 were hyperthyroid state, 25 were euthyroid, 10 were hypothyroidism and 4 were T-3thyrotoxicosis. 2. Among the 45 cases of hyperthyroid state, 27 were hyperthyroidism, 17 were simple goiter and 1was thyroid cancer. 3. The patient in hyperthyroidism was appeared from preschool age and progressively increasedin number of patients with the age. 4. Among 10 cases of hypothyroidism, 7 were juvenile myxedema, 2 werecretinism and 1 was thyroid cancer. 5. 4 cases of T-3 thyrotoxicosis were present, right early hyperthyroidism.They were appeared over the 10 years of age. 6. 3 cases of thyroid cancer were present, of each 1 was normalfunctioning, other one was hypofunction and the 3rd was hyperfunctioning thyroid cancer. The later one is veryrare thyroid cancer especially in childhood and adolescent. They were confirmed histologically as papillaryadenocarcinoma. 7, The incidence of thyroid disease in childhood was about 2.5 times more common in female than inmale, among 60 cases of all thyroid disease, 43 were female and 17 were male.