Many women regularly experience or have experienced menstrual pain before. For some women, despite continuously seeking answers to explain this pain, their physician may not be able to easily determine the cause. Endometriosis, often a very painful disorder, is fairly common, but is extremely difficult to diagnose and treat. More than 5.5 million American women have symptoms of endometriosis, and it is estimated to affect approximately 10 percent of reproductive-aged women. What is endometriosis? Endometriosis is a condition in which tissue that normally lines the uterus, called the uterine