Fine needle aspiration(FNA) has been quite successful in identifying benign and malignant breast lesions, but a "gray zone" exists. A total of 697 FNAs of breast were performed at Korea Cancer Center Hospital for a period of one year. One hundred and eleven of the 697 FNAs were diagnosed as atypical or suspicious for malignancy. Among them, we reviewed 74 FNAs, un which histologic diagnoses were made, and applied cytologic grading system proposed by Masood et al (1990) to evaluate the usefulness of this system in minimizing the size of gray zone. Technical problem was responsible for equivocal diagnoses in 19 FNAs Of the remaining 55 FNAs, 18 were benign and 37 were malignant. Among benign conditions, fibroadenoma(5 cases) and fibrocystic disease with fibroadenomatous feature(3 cases) constituted the largest groups. The majority of malignant conditions were infiltrating ductal carcinoma(29 cases), however, those low grade carcinomas Including tubular carcinoma(3 oases), cribriform carcinoma(2 cases), and mucinous carcinoma(2 cases) occupied a relatively large proportion Cytologic grading system was quite useful in minimizing the size of gray lone. The scores of 27 out of 29 usual infiltrating ductal carcinomas belonged to the group of cytologic malignancy, how-ever, only 2 out of 7 low grade carcinomas got scores of malignancy FNA from fibroadenoma or fibrocystic disease with fibroadenomatous features showed a tendency toward high scores. Experience of the cytopathologist and familiarity with cytologic alteration in breast disease cannot be overemphasized.