Abstract: A group of 325 female patients with fibrocystic breast disease comtirmed by biopsy were analyzed The breast lesions were classified into three grades accord ing to the epithelial hyperplasia degree of duct or acirus, of these, Grade Ⅰ was 251 cases (77.20%), Grade Ⅱ 53 cases (16.3%), Grade Ⅲ 16 cases (4.90%) and the rest 5 cases had early malignant transformation. After 2 to 7 years followed-up, 28 cases had performed another biopsy, 4 of them occured malignant transformation. we concluded: the extention of atypical hyperplasia may aggravated concomitantly with the age increasing, the frequent age interval of malignant transformation was 40.