Fibrocystic disease of the breast has been generally regarded as a disorder due to either excess hormonal stimulation or an exaggerated proliferative response by hypersensitive breast epithelium. The unique lobular lesion-adenosis- and its variants have been regarded as non-neoplastic and non-preneoplastic glandular hypertrophy and hyperplasia, and have different organoid patterns and origins. We have examined a total of 242 cases previously diagnosed as 'fibrocystic disease' at the Department of Pathology with the purpose of clarifying the variants of adenosis in detail and refining the infinitely large 'fibrocystic disease' classification as non-proliferative fibrocystic change and proliferative disorders, such as epitheliosis and atypical hyperplasia. In this study, 224 cases (92.5%) were nonproliferative disease, mostly adenosis (40.1%), and 18 cases (7.5%) were proliferative disease, which consisted of moderate to florid hyperplasia and epitheliosis.