Objective: To evaluate the role of transvaginal power Doppler sonography to discriminate between benign and malignant endometrial conditions in women presenting with postmenopausal bleeding and thickened endometrium at baseline sonography. Methods: Ninety-one postmenopausal women (median age, 58 years; range, 47-83 years) presenting with uterine bleeding and a thickened endometrium (≥ 5-mm double-layer endometrial thickness) on transvaginal sonography were included in this prospective study. Endometrial blood flow distribution was assessed in all patients by power Doppler immediately after B-mode transvaginal sonography. Three different vascular patterns were defined: Pattern A: multiple-vessel pattern, Pattern B: single-vessel pattern and Pattern C: scattered-vessel pattern. Histological diagnoses were obtained in all cases. No patient taking tamoxifen citrate or receiving hormone replacement therapy was included. Results: Histological diagnoses were as follows: endometrial cancer: 33 (36%), endometrial polyp: 37 (41%), endometrial hyperplasia: 14 (15%), endometrial cystic atrophy: 7 (8%). Blood flow was found in 97%, 92%, 79% and 85% of cases of carcinoma, polyp, hyperplasia and endometrial cystic atrophy, respectively. A total of 81.3% of vascularized endometrial cancers showed Pattern A, 97.1% of vascularized polyps exhibited Pattern B and 72.7% of vascularized hyperplasias showed Pattern C. Sensitivity and specificity for endometrial cancer were 78.8% and 100%. For endometrial polyp these respective values were 89.2% and 87% and for hyperplasia they were 57.1% and 88.3%. Conclusions: Transvaginal power Doppler blood flow mapping is useful to differentiate benign from malignant endometrial pathology in women presenting with postmenopausal bleeding and thickened endometrium at baseline sonography. Copyright © 2003 ISUOG. Published by John Wiley & Sons, Ltd.