Risk factors for breast cancer are related to endogenous hormonesand reproductive events. As such, traditional cancer prevention strategies arenot easily applicable. Tamoxifen and other selective estrogen receptormodulators (SERMs) offer a new preventive strategy for some high-risk women,but have not yet been shown to be efficacious for all women. New tools toidentify high-risk women are needed. One such tool is the development of amultigenic model of breast cancer susceptibility that can be used to screenwomen in order to identify those who carry a combination of alleles that putsthem at significantly increased risk.