Sonohysterography is superior to unenhanced transvaginal sonography in specifying the abnormal ultrasonographic appearance induced by prolonged tamoxifen therapy, it is easily performed, cost-effective and very well tolerated by the patients with no complications. Sonohysterography is recommended as a minimally invasive diagnostic tool for the assessment of endometrial changes in asymptomatic postmenopausal breast cancer patients on long-term tamoxifen therapy with thickened endometrium or inadequately visualized endometrial echo on transvaginal sonography.