Study Objective: We sought to determine whether relief of chronic pelvic pain symptoms with hormonal treatment is predictive of presence or absence of endometriosis or location of endometriosis within the pelvis. Design: A retrospective, chart review (Canadian Task Force classification II-3). Setting: A private practice endometriosis referral center. Patients: Patients undergoing laparoscopy for pelvic pain with at least 3 months of previous hormonal treatment. Interventions: Laparoscopy. Measurements and Main Results: Response to hormonal treatment was ascertained by patient report in medical records. Presence and location of endometriosis was recorded based on operative findings and pathology reports. In all, 486 patients with chronic pelvic pain were identified, of whom 104 met our inclusion criteria. Endometriosis was diagnosed at laparoscopy in 88 (85%) patients. Endometriosis was identified at laparoscopy in 46 (81%) of 57 patients who failed to respond to hormonal therapy compared with 41 (87%) of 47 patients who previously responded to hormonal therapy (p = .37). Using final pathology as basis of diagnosis, 31 (67%) of 46 responders, and 39 (68%) of 57 nonresponders had endometriosis (p = .91). When data were analyzed by anatomic site of endometriosis, no significant difference was noted in response to preoperative hormonal therapy. Conclusion: Relief of chronic pelvic pain symptoms, or lack of response, with preoperative hormonal therapy is not an accurate predictor of presence or absence of histologically confirmed endometriosis at laparoscopy. Patients with chronic pelvic pain may benefit from laparoscopy and no judgment regarding diagnosis should be made without this evaluation. © 2008 AAGL.