Objective: To differentiate benign from malignant ovarian tumors based on sonographic detection of a solid component. Method: Sixty-three women with ovarian masses were evaluated preoperativety by grayscale and power/color Doppler ultrasonographic examination, with specific predefined criteria for the solid component. Sensitivity, specificity, and positive and negative predictive values were calculated and assessed against the histopathologic outcome. The contribution of cancer antigen (CA) 125 levels to the diagnostic accuracy was also assessed. Result: Sensitivity, specificity, and positive and negative predictive values were 100%, 95.2%, 91.3% and 100%, respectively, with two false-positive results. Had an elevated CA 125 level (>35 U/mL) been included in the malignancy criteria, the false-positive results would have been eliminated, giving an accuracy of 100%. Conclusion: Sonographic evaluation with predefined specific criteria for the detection of a solid tumor component is an accurate method of preoperative discrimination between benign and malignant ovarian tumors. A serum CA 125 assay may assist in eliminating false-positive results. (c) 2005 International Federation of Gynecology and Obstetrics. Published by Elsevier Ireland Ltd. All rights reserved.