Pelvic Pain in Women With Endometriosis

* INCLUSION CRITERIA: Women between the ages of 18 and 50 years, who have their reproductive organs. Those undergoing tubal ligation must be at least 21 years old. Excellent health other than a three-month history of pelvic pain and documented endometriosis at laparoscopy. Chronic medications may be acceptable at the discretion of the Principal Investigator (PI). Use of antidepressants, medications for migraines and headaches, allergy medications, and treatment of bowel symptoms such as irritable bowel disease will be allowed. Do not desire pregnancy for the duration of the study. Are using abstinence, mechanical (condoms, diaphragms) or sterilization methods of contraception and are willing to continue using them throughout the study. Willing and able to give informed consent. Willing and able to comply with study requirements. BMI \< than 32 kg/m\^2. History of regular cyclic menses. EXCLUSION CRITERIA: Women with other causes of chronic pelvic pain including infectious, gastrointestinal, psychologic disorders, fibromyalgia and chronic fatigue syndrome. Significant abnormalities in the physical or laboratory examination including renal and liver function more than twice the normal range. Hysterectomy or bilateral salpingo-oophorectomy. Pregnancy. Lactation. Use of hormonal contraception, selective estrogen receptor modulators, progestins, estrogens, steroids, or ovulation induction in the last 3 months. Other medical or surgical treatment for endometriosis in the last 6 months. Untreated abnormal pap smear or other gynecologic condition. Manic-depressive illness or untreated major depression. HIV infection.