Objective: The aim of this study was to evaluate the ability of four risk of malignancy indices (RMI) to detect malignant ovarian tumors. Methods: This is a prospective study of 100 women admitted to the Department of Obstetrics and Gynecology of Gulhane Military Medicine Academy for surgical exploration of pelvic masses. To diagnose malignant ovarian tumors, the sensitivity, specificity, negative and positive predictive values and diagnostic accuracy of four RMIs (RMI 1, RMI 2, RMI 3, and RMI 4) were obtained. Results: In our study we found that there is no statistically significant difference in the performance of four different RMIs in discriminating malignancy. We think that malignancy risk indices is more reliable than the menopausal status, serum CA-125 levels, ultrasound features and tumor size separately in detecting malignancy. Conclusion: We concluded that any of the four malignancy risk indices described can be used for selection of cases for optimal therapy. These methods are simple techniques that can be used even in less-specialized gynecology clinics to facilitate the selection of cases for referral to an oncological unit. © 2011. Asian Society of Gynecologic Oncology, Korean Society of Gynecologic Oncology and Colposcopy.