Objective To investigate the surgical effort of endometriosis the in the surgical management of early ovarian cancer. Design: A retrospective study Setting National Cancer Center Population All women who underwent cytoreductive surgery between January 2001 and July 2008 Method: Retrospective medical chart review Main Outcomes Measure Requirement of the rectosigmoid colon and pathological outcome of resected the rectosigmoid colon Results: Of the 37 stage I and 15 stage II ovarian cancer women, twelve cases (23.1%) were serous carcinomas and 40 (76.9%) were non-serous carcinomas (9 mucinous, 11 endometrioid, 14 clear cell, 2 transitional cell, and 4 mixed carcinomas). Co-existence of endometriosis was identified in 28.8% of the patients at adnexa, pelvic peritoneum, and rectum. Resection of the rectosigmoid colon to completely resect all suspicious lesions was required in 15 patients (28.8%). Cancer and endometriosis were identified in 6 (40%) and 5 (33%) patients, respectively. Fibrosis and/or adhesion were identified in 4 (27%) patients. Complications related resection of the rectosigmoid colon such as fistula or leakage were not identified with a median follow up of 50 months. Conclusions: Resection of the rectosigmoid colon with adjacent pelvic peritonectomy is required in approximately one-third of the patients with early ovarian cancer for complete removal of all suspicious metastatic lesions in the pelvis. Cancer invasion, endometriosis, and fibrosis and/or adhesion are the causes to perform resection of the rectosigmoid colon in such patients.