Borderline ovarian tumours are rare and occur mostly in younger women than ovarian cancer. The improved knowledge of histologic and comportmental patterns since the last twenty years has permitted to drastically decrease the therapeutics of these tumours which remains mostly surgical. Conservative surgery is possible in young women who desire fertility sparing treatment. Chemotherapy is only indicated in more aggressive BOT: serous invasive implants and eventually pseudomyxoma peritonei. According to their low mitotic activity, a long follow-up is required to detect the potential recurrences of such tumours. These recurrences mostly occur on the same histologic patterns as initially diagnosed and are often cured by surgery only.