This study is being done to find out what factors may be related to the risk of getting a second breast cancer among women who already have breast cancer in one breast. It will look at how genes, treatment for breast cancer; including radiation therapy, and the effects of different lifestyle activities, may affect the risk of breast cancer. It will use different processes to find genes that might increase the risk of breast cancer. The results of this study may help to develop better ways to detect, treat and prevent breast cancer. This study will compare women who have breast cancer in both breasts to women who have breast cancer in only one breast.