This contract is to assess the new third-generation SERM, Bazedoxifene, alone and in combination with CE and/or an AI, to prevent mammary carcinogenesis induced in virgin female Sprague-Dawley rats by N-methyl-N-nitrosourea (MNU). The tasks will involve optimizing the dose and timing of BZA administration, and PK profile of BZA in combination with the AI.