Borderline ovarian tumor is an epithelial ovarian tumor that occurs in patients younger than those with an epithelial ovarian cancer. In contrast with invasive epithelial ovarian cancer, borderline ovarian tumor presents as an excellent survival rate and a characteristic low incidence of recurrence. However, there are some risk factors for recurrence including advanced stage, micropapillary histology, microinvasion, invasive implants, conservative treatment, aneuploid DNA ploidy, old age, suboptimal debulking, and an elevated preoperative CA125 level in women with borderline ovarian tumor. Long term and close follow up of these patients is required because recurrences can develop years after primary operation.