One hundred two postmenopausal women underwent ultrasonographic evaluation of adnexal masses before surgery. Twenty-nine (28%) had malignant tumors and 73 (72%) had benign tumors. Two of 33 patients with a “simple cyst” smaller than 5 cm in diameter by ultrasound had malignant ovarian tumors. Twenty-two of the 52 women (42%) with “complex masses” by ultrasound and five of the 17 (29%) with solid tumors had ovarian cancer. For predicting malignancy in ovarian tumors, abdominal ultrasonography had a positive predictive value of 39% and a negative predictive value of 94%. If a negative sonogram had been relied upon, 6% of malignant ovarian tumors in postmenopausal women might have been missed.