OBJECTIVE: In vitro studies demonstrated that implantation on membranes (peritoneum, amniotic membranes) can take place if there are defects on the surface of the membranes. If these mechanisms play a role for the development of endometriosis in vivo, then patients with surgical treatment of peritoneal endometriosis in the luteal phase must have a high recurrence rate. DESIGN: Retrospective analysis of operation charts and follow-up data. SETTING: Department of gynecology, in a hospital-based endometriosis treatment center. PATIENT(S): Two hundred twenty premenopausal women. INTERVENTION(S): Laparoscopic treatment for peritoneal endometriosis, stage I and II by revised American Society for Reproductive Medicine guidelines. MAIN OUTCOME MEASURE(S): During the follow-up period of 2 years, symptoms and gynecological and sonographic findings were documented. In case of suspected recurrence a repeat laparoscopy with biopsy was performed to prove the recurrent endometriosis macroscopically and histologically. RESULT(S): The total recurrence rate after 2 years was 9.6%. The recurrence rate of group III (15%) was twice as high as those of group I (7%) and group II (8%), as indicated by subjective complaints, clinical findings, macroscopy, and histology; no differences were found between groups I and II. CONCLUSION(S): Endoscopic surgery for the treatment of peritoneal endometriosis should not be performed in the luteal phase.