Many women with pelvic pain have endometriosis, a condition in which tissue from the uterine lining (endometrium) is also outside the uterus. Endometriosis pain often returns after medical treatment is stopped. Surgical therapies have had varied success in reducing pain, with laparoscopic excision of implants one of the most effective methods. Raloxifene (Evista (Trademark), Lilly), has been approved by the Food and Drug Administration for use in preventing bone loss in postmenopausal women. This compound has effects that are both similar to and different from those of the hormone estrogen. Unlike estrogen, raloxifene does not stimulate growth of the uterus or breast tissue in post-menopausal women. If raloxifene blocks estrogen action in the lining of the uterus (or endometrium) of reproductive age women, as it does in postmenopausal women, it may also limit growth of endometriosis and prevent the return of pain. This phase II randomized placebo-controlled study evaluates whether surgery followed by daily administration of raloxifene for six months reduces pain for a longer time than surgery alone.