Objective: To clarify the rate of major intra-operative and post-operative complications experienced during excisional surgery for endometriosis. Design: Prospective multi-centre observational study set in two University teaching hospitals and three private hospitals in Sydney, Australia. All consecutive subjects undergoing laparoscopic excisional surgery for minimal to severe endometriosis were recruited (790 subjects). Complications were recorded intra-opera- tively or post-operatively on a secure computerised patient database. Major intra-and post-operative complications i.e. inadvertent visceral or vascular injury or other complications directly related to surgery that either significantly prolonged the operating time, delayed discharge or necessitated re-admission. Results: Seven hundred and ninety subjects were recruited over a 3-year period. Seven major complications were experienced (8.8/1000); four bowel injuries, one cystotomy, one ureteric transection, and one major vascular injury. All visceral or vascular injuries were diagnosed prior to completion of the surgery. No significant longterm sequelae were experienced. Conclusion: The incidence of major complications in this study of 8.8/1000 compares favourably with other similar reports. In view of the potential symptom relief obtained, the authors continue to believe the benefits of such surgery significantly outweigh the risks of subsequent operative-related morbidity. Objective: To clarify the rate of major intra-operative and post-operative complications experienced during excisional surgery for endometriosis. Design: Prospective multi-center observational study set in two University teaching hospitals and three private hospitals in Sydney, Australia. All consecutive subjects undergoing Major intra-and post-operative complications ie in advertent visceral or vascular injury and other (790 subjects). complications directly related to surgery that either significantly prolonged the operating time, delayed discharge or necessitated re-admission. Results: Seven hundred and ninety subjects were recruited over a 3-year period. Seven major complications were experienced (8.8 / 1000); four bowel injuries, one cystotomy, one ureteric transection, and one major vascular injury. All visceral or vascular injuries were diagnosed prior to completion of the surgery. No significant longterm sequelae were experienced. Conclusion: The incidence of major complications in this study of 8.8 / 1000 fav favrably with other similar reports. In view of the potential symptom relief obtained, the authors continue to believe the benefits of such surgery significantly outweigh the risks of subsequent operative-related morbidity.