Breast cancer is the most common non-skin cancer and the second leading cause of cancer death in North American women. Mammography is the only screening test shown to reduce breast cancer-related mortality. There is general agreement that screening should be offered at least biennially to women 50 to 74 years of age. For women 40 to 49 years of age, the risks and benefits of screening should be discussed, and the decision to perform screening should take into consideration the individual patient risk, values, and comfort level of the patient and physician. Information is lacking about the effectiveness of screening in women 75 years and older. The decision to screen women in this age group should be individualized, keeping the patient's life expectancy, functional status, and goals of care in mind. For women with an estimated lifetime breast cancer risk of more than 20 percent or who have a BRCA mutation, screening should begin at 25 years of age or at the age that is five to 10 years younger than the earliest age that breast cancer was diagnosed in the family. Screening with magnetic resonance imaging may be considered in high-risk women, but its impact on breast cancer mortality is uncertain. Clinical breast examination plus mammography seems to be no more effective than mammography alone at reducing breast cancer mortality. Teaching breast self-examination does not improve mortality and is not recommended; however, women should be aware of any changes in their breasts and report them promptly.