Clinical features of 147 patients with biopsy-proven thyroid carcinomas were investigated from January, 1972 to April, 1978 at the Seoul National University Hospital with the following results. 1) The incidence of thyroid carcinomas according to their histopathological classification revealed 76.2% of papillary carcinoma, 19.0% of follicular carcinoma, and 3 cases of occult sclerozing carcinoma, 1 case of giant cell carcinoma and 1 case of metastatic melanoma. 2) The ratio of male to femle patients was 1:8.3 and showed no difference between papillary and follicular carcinomas. 3) The age distribution showed the peak incidence in the fourth decade (29.3%) followed by the fifth and sixth decades. 4) The average duration of illness from the onset of symptoms was about 5 years while it was 4.4 years and 7.6 years in the papillary and follicular carcinomas respectively. 5) The diameter of the thyroid masses was smaller than 5cm in 53.6% of the patients, from 5cm to 10cm in 40.0% and larger than 10cm in 6.4%. 6) In 36.4% of the patients with thyroid carcinomas the thyroid masses were fixed to adjacent tissues. 7) Metastasis to the regional lymph nodes was noted in 40.0% of the total cases, and in 45.2% and 17.6% of the papillary and follicular carcinomas respectively, while the lung and bone metastases were found in 10.0% and 4.4% in each type respectively. 8) 88.9% of the patients showed cold areas in the thyroid scans using 131I. 9) Typical psammoma bodies were observed in 21.3% of the cases in the microscopic examination of the pathological specimens. 10) The initial diagnosis of thyroid malignancy could be made before histological confirmation in 64.5% of the patients. 11) The clinical staging slightly modified from Schulz method revealed 43.6% of the patients in stage I, 26.4% in stage Ⅱ, 20.9% in stage Ⅲ and 9.1% in stage Ⅳ. 12) The association with Hashimoto's thyroiditis was noted in 4 cases, with nodular goiter in 3 cases, and with follicular adenoma in 1 case.