Our purpose is to quantify mammary epithelial lesions in large numbers of biopsy size samples of human breast tissue using our own histological grading methods and to correlate the findings with risk as determined by other histological methods, by mammography, and by the actual appearance of cancers in the patients studied. Differential counts of different kinds of lesions are determined, and these are scored according to severity and amount of atypia, which can be further related to area of tissue on the slides.