This study was undertaken to evaluate the clinical features and survival outcomes of ovarian cancer patients whohad associated pelvic endometrioisis. The medical records of 1076 patients with ovarian cancer treated at ChiangMai University Hospital between 1995 and 2005 were reviewed. Among of these patients, 37 (3.4%) had associatedpelvic endometriosis. The mean age of the patients was 44 years (25-62 years). The most common presenting signand symptom was an abdominal mass (12), followed by abdominal pain (10), abdominal distension (7), abnormaluterine bleeding (2). Twenty-one (56.8%) patients were nulliparous and 14 (37.8%) were single. The stage distributionwas stage I (24), stage II (4), stage III (4), and stage IV (1). Four patients had 2 primary carcinomas. The mostcommon histology of the 37 patients was clear cell carcinoma (17) followed by endometrioid carcinoma (11). Theestimated 5-year disease - free survival was 55.4%. In conclusion, most patients associated with endometriosisassociatedovarian carcinoma present with abdominal masses and pain. Clear cell CA is the most common histologyin ovarian cancer patients who have associated endometriosis. Three fourths of the patients are in stage I and havefavorable prognosis.