Endometriosis is a disease that is associated with severe pelvic pain and is a major cause of infertility in women. It is an enigmatic disease whose etiology and pathophysiology has been studied to a limited extent. The events associated with the establishment of the disease and mechanisms associated with infertility are difficult to assess in a systemic manner in women. In order to understand the early and progressive events associated with the establishment of the disease, we have developed a baboon model in which the disease can be induced. This induction manifests itself in a manner that recapitulates the spontaneous disease. The advantage of the induced model is that the progressive changes in both the ectopic and eutopic endometrium can be studied in a nonhuman primate model at specific times during the menstrual cycle and as the disease process continues.