Borderline ovarian tumours (BOT) are a group of ovarian epithelial tumours defined by atypical epithelial proliferation without stromal invasion. Recurrence and malignant transformation can occur. Our aim was to determine the clinical, epidemiologic and histological features of the BOT by a retrospective coorte study involving 79 patients diagnosed with BOT and treated at IPO-Coimbra Between 1990-2016. After a mean follow up of 5, 9 years, we reported 4 cases of relapse, 3 with malignant transformation to invasive ovarian cancer. The overall survival at 5 and 10 years was respectively of 100% and 96, 2%. Ca125, FIGO stage and extra-ovarian peritoneal implants were associated to disease recurrence. Neither micropapillary growth pattern nor age showed that association. It is essential to standardize the clinical practice in different hospitals.