Purpose: The aim of this study was to evaluate prognostic values of the risk of malignancy index (RMI)/1-4 in patients with borderline ovarian tumors (BOTs). Methods: The study consisted of 50 patients with BOT diagnosed and treated between 2005-2010 and 50 patients with benign adnexal massses between 2009-2010 as a control comparison group in the retropsective study. Preoperative serum CA125, U score, tumor size (S), and menopausal status were recorded. The RMI 1-3 was calculated according to the formula; U × M × CA125 and RMI 4 formulation was; U × M × CA125 × S. S equaled 1 for tumor size <7 cm and was 2 when size ≥7 cm. The RMI 1-4 indices were calculated for all patients together with the sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and diagnostic accuracy (DA). The performances of RMI indices were evaluated by McNemar’s test and determined the best score cutoff value by the receiver operating characteristic (ROC) curve. Results: The mean age, median value of CA125, ultrasound score, menopausal status, median values of RMI 1-4 of BOTs were statistically higher than benign adnexal masses. The sensitivity of RMI 1-4 was 26, 36, 62, and 60% at cutoff 200 level, respectively. The areas under curve of RMI 1-4 were found to be 0.676, 0.665, 0.668 and 0.734, respectively. DA of RMI 1-4 was found to be 56, 59, 50, and 71, respectively. When RMI 1-4 indices were compared with each other RMI 4 was the best RMI for BOTs. Conclusion: RMI 4 was the best predictive RMI for preoperative discrimination of BOT at a cutoff level of 200.