Endometriosis remains a diagnostic and therapeutic challenge despite decades of clinical experience and research. The multiple treatment options for endometriosis described in this symposium clearly indicate how difficult it can be to diagnose and effectively treat endometriosis with our current understanding of the disease. At least 3 major challenges to our understanding can be identified: (1) endometriosis does not always cause pain; (2) other causes of pelvic pain often coexists in patients with endometriosis; and (3) common medical and surgical treatments for endometriosis are relatively nonspecific. Insights from the articles in this symposium can help clinicians reach a new level of understanding of endometriosis and perhaps lead to more effective methods for diagnosing and treating this perplexing condition.