Breast cancer is the most common invasive cancer in women globally, and it affects more than 1 million women worldwide each year. It is a preventable disease in part, and primary care providers and public health programs play a key role in providing cancer preventive care. There are several health behaviors that may reduce the risk of breast cancer, including prolonged lactation; regular physical activity; avoiding overweight, obesity, and lifetime weight gain; avoiding excess alcohol intake; avoiding prolonged use of exogenous hormone therapy; and avoiding excessive radiation. These behaviors, although they have not been proven in clinical trials to reduce risk, are likely to be beneficial; information on them can be provided as a prevention strategy in countries of diverse means, although the methods of information delivery and follow-up will depend on financial and personnel resources. Many of these health behaviors can reduce the risk for other chronic diseases and, thus, may be of great interest for general public health. In high resource level countries, additional prevention methods are available for high-risk women, including selective estrogen response modulators and, for women at very high risk, bilateral prophylactic mastectomy and bilateral oophorectomy. Most women can benefit from advice and preventive care for reducing their risk for breast cancer. Cancer 2008;113(8 suppl):2325–30. © 2008 American Cancer Society.