Folate is a water-soluble B-vitamin and is an important cofactor in one-carbon metabolism. This vitamin plays an important role in the pathogenesis of several chronic diseases. In recent years, there has been much interest in the relationship between folate status and breast cancer risk, particularly given the dramatic increase in dietary intake and blood serum folate levels in North America as a result of mandatory folic acid fortification and the widespread use of folic acid supplementation. The well-described dual effects of folate on carcinogenesis underscore the need to clarify the role of folate in the development and progression of breast cancer. This is of particular importance among those at high risk of developing breast cancer because of benign breast disease, a strong family history of breast cancer or an inherited mutation in BRCA1 or BRCA2. BRCA mutation carriers face a high lifetime risk of developing breast cancer, estimated at 80 % compared with 11 % in the general population. Predictive genetic testing permits the identification of these high-risk women prior to diagnosis; however, prevention is limited to surgery and chemoprevention, and the importance of modifiable risk factors such as diet and lifestyle has not been elucidated. Our goal is to develop practical and safe interventions for high-risk women leading to a decrease in the number of breast cases and deaths attributed to breast cancer.