This study was developed to see if surgery followed by daily doses of Raloxifene (Evista) is effective in reducing pain, for a longer time than surgery in combination with a placebo (inactive "sugar pill") treatment. Raloxifene acts like estrogens in some tissues and not like estrogens in others. Postmenopausal women receiving Raloxifene for the prevention of osteoporosis had an increase in bone density and an improvement of their blood lipids (fat content in the blood). However, unlike estrogen, Raloxifene does not promote the growth of breast tissue or the uterus. If Raloxifene blocks estrogen action in the lining of the uterus (endometrium) of reproductive age women, as it does in post-menopausal women, it may also limit the growth of endometriosis and prevent the return of pain.