The main objectives of this study are to determine the individual and combined effects of Raloxifene and omega-3 fatty acids on surrogate markers of breast cancer development in healthy, postmenopausal women. The primary endpoint will be mammographic density for which the study has been powered. Breast density is a major risk factor for breast cancer and hence it is chosen to evaluate the potential chemopreventive efficacy of our interventions. Secondary endpoints would include markers of oxidative stress, parameters of estrogen metabolism, markers of inflammation, and markers of IGF-I signaling, all of which have been shown in the literature to have an influence on mammary carcinogenesis.