113 patients with nodular goiter were studied cytologically by needle aspiration for differential diagnosis at the department of internal medicine, Chung Nam National University Hospital since October 1980 till July 1981, and the final diagnosis taken from biopsies were compared with the cytologic method on the 44 cases who received operation. The results were obtained as follows: 1. Among the 113 cases of total patients, male were 15 cases (13.3%) and female were 98 cases (86.7%) and the sex ratio (M:F) was 1 : 6.5. The peak age incidence was in the third decade followed by forth and second decades. 2. The findings of cytological diagnosis in 113 cases showed benign adenoma in 69 cases (61.1 %), Subacute and chronic thyroiditis in 22 cases(19.5%), papillary carcinoma in 15 cases (13.3%) and follicular carcinoma in 7 cases (6.2%), respectively, and 48 cases (69.6%) of the.adenomas and 2 cases(9.1%) of papillary carcinomas showed combined cystic degeneration of the nodules. 3. The diameter of the nodules by palpation revealed within $2sim5cm$ in 88 cases (77.9%) out of 113 cases, below 2 cm in 17 cases and over 5cm in 8 cases and there were no significant relationship between the size of the nodule and disease entity. 4. The findings of thyroid scintigram using $^{131}I$ in 113 cases of nodular goiter showed "cold nodule" in 111 cases (98.2%) and normal scan (radioactivity) in 2 cases (1.8%) which showed adenoma in cytology and there was no cases with "hot nodule". 5. The thyroid functions of the 113 cases revealed as euthyroidism in 108 cases (95. 6%), hypothyroidism in 2 cases (1.8%) who showed chronic thyroiditis and hyperthyroidism in 3 cases (2.7%) in adenomas but there was no evidence that the nodules of the above 3 cases were the reason of hyperthyroidism. 6. In 44 operated cases, the histological diagnosis revealed 23 cases of adenoma out of 27 cases(85.2%) who were diagnosed as adenoma by cytology and 15 cases of malignancy out of 17 cases (88.2 %), and the overall diagnostic accuracy of aspiration cytology was 86.4 %.