Borderline ovarian tumors account for approximately 15% of all epithelial ovarian tumors. In the early 1970s, borderline tumors were categorized as either serous or mucinous with overall survival rates of 75–90%. Since then, it has been recognized that the two categories are heterogonous. There are now many different groups following the recognition of serous tumors with microinvasion, non-invasive and invasive peritoneal implants and a micropapillary pattern, and of mucinous tumors with microinvasion, intraepithelial carcinoma and pseudomyxoma peritoneal implants, in addition to further delineation of endometrial, clear cell and transitional cell tumors with atypical proliferation. This review outlines the most recent information regarding the epidemiology, pathology and clinical management of borderline tumors. Surgical management to excise all visible tumors remains the cornerstone of therapy. Because borderline ovarian tumors often occur in reproductive-age women, fertility is an important issue. Conservative surgery is a safe in carefully selected patients. Effective non-surgical therapies are yet to be identified.