In 20 cases of histologically proved endometrial cancer the depth of myometrial invasion was ascertained by means of transvaginal ultrasound, using a high-frequency endocavitary probe. The sonographic findings were confirmed by histologic examination in 18 of the 20 patients evaluated (90.0%). Transvaginal ultrasound provides a fuller preoperative clinical picture and supplies additional diagnostic information which is invaluable in the choice of therapeutic approach.