Accurately defining a patient's risk of developing breast cancer is a challenging endeavor. Many factors have been implicated in the causation of breast cancer and quantifying them is difficult. Risk stratification is performed using population models, such as the Gail model, as well as the patient's personal and family history and genetic testing. The clinician who is facile with these components will not only be able to identify those patients at highest risk for whom heightened surveillance is recommended, but also to allay the fears of the average-risk patient and provide them reassurance. Patients who are at very high risk of developing breast cancer are BRCA1 or BRCA2 gene mutation carriers, those with a personal history of atypical ductal hyperplasia or lobular carcinoma in situ with associated family history, those who have undergone therapeutic or similarly significant radiation exposure, and those with a history of a BRCA1 or BRCA2 gene mutation in the family of an untested individual. Patients with an elevated risk, but not in the very high risk category, are those with a family history of breast cancer, personal history of breast cancer, significantly dense breast tissue, hormone replacement therapy longer than 10 years, and a history of atypical ductal hyperplasia or lobular carcinoma in situ without family history of breast cancer. Risk-reducing strategies include chemoprevention with tamoxifen or raloxifene and surgical prophylaxis with bilateral prophylactic mastectomy and/or bilateral salpingo-oophorectomy. A high-risk surveillance regimen includes annual mammography, annual magnetic resonance imaging in selected individuals, and semiannual clinical breast exams.