OBJECTIVE: To outline modern principles of surgery, radiation therapy, and systemic treatment of breast cancer, and to review preliminary data on breast cancer prevention. QUALITY OF EVIDENCE: A MEDLINE search was conducted from 1966 to the beginning of 1999; most of the studies reviewed are randomized clinical trials. MAIN MESSAGE: Breast conservation surgery should be offered to all women with early breast cancer because studies demonstrate survival rates equivalent to those with mastectomy. If mastectomy is chosen, breast reconstruction should be offered. Most women with breast cancer are treated systemically with either chemotherapy or tamoxifen, or both, and mortality is substantially reduced. Data indicating that tamoxifen prevents breast cancer are promising; more studies with both tamoxifen and raloxifene are under way. All women should be strongly encouraged to enter clinical trials. CONCLUSIONS: Because many issues face women recently diagnosed with breast cancer, they often seek out family physicians as advisors to help negotiate a complex treatment path. The possibility of preventing breast cancer will undoubtedly raise questions among family members of women with breast cancer that should appropriately be answered and referred, if necessary, by family physicians.