Abdominal and particularly vaginal sonography are useful diagnostic techniques for evaluating endometrium. Endometrial thickness can be measured and the echo pattern of the different parts of endometrium analysed. During normal cycles a triple line sign is typical for the late proliferative and periovulatory phase. In the secretory phase the endometrium is echogenic and posterior enhancement of echoes can be seen. It is also useful to control the effects of hormonal treatments or the endometrium using sonography. In postmenopausal women endometrial thickness of 4-5 mm or more is abnormal and further evaluations are indicated. In endometrial cancer sonography is a reliable way to estimate myometrial invasion.