In examinations where the etiology of an abnormal endometrial sonographic image is not clear, saline infusion through a fine flexible catheter during transvaginal sonography provides visual contrast and uterine expansion. In 39 women, polyps, myomata, synechiae, endometrial hyperplasia, and cancer were correctly described as verified at surgery. Hyperplasia and neoplasia are not distinguishable, but the approach for biopsy and therapy is established by this simple and well-tolerated technique, which is here called sonohysterography.