Women who are at high risk for breast cancer, either because of linkage to high risk breast and ovarian cancer families, or because of a carcinoma in the opposite breast, will be studied. Women will have a physical examination and mammography to ensure that no breast abnormalities are present. Eligible women will undergo biopsy of the breast to obtain normal breast tissue. Short-term cell cultures will be established from this tissue and early passages of the short-term cell lines will be stored. A bank of high risk normal mammary epithelial cells will be established. To further characterize the mammary epithelial cells in this population of women, cell cultures will subsequently be analyzed for their growth and metabolic properties, sensitivity to chemopreventive agents, steroid receptor characteristics, oncogene expression and regulation, and genetic changes.