Endometrial sampling is the mainstay of management of the postmenopausal patient with uterine bleeding. Thirty women with postmenopausal bleeding were studied prospectively. Before endometrial sampling, a vaginal probe ultrasonographic examination was performed. Eleven patients demonstrated a thin "pencil line" endometrial echo in which the maximum anteroposterior thickness on the long axis view was less than or equal to 5 mm. All eleven patients had minimal tissue obtained on biopsy and a pathology report of "tissue insufficient for diagnosis." Seventeen patients had an echogenic endometrium greater than or equal to 6 mm. Pathology reports of their samples revealed tissue insufficient for diagnosis (two cases), proliferative endometrium (six), secretory endometrium (three), hyperplastic endometrium (three), polyp (two), and endometrial cancer (one case). Two additional patients had no endometrial echo visualized because of associated myomas. These findings suggest (1) that the absence of significant endometrial tissue (echo less than or equal to 5 mm) on vaginal ultrasonography in cases with postmenopausal bleeding is uniformly associated with tissue insufficient for diagnosis, and (2) when endometrial thickness is greater than or equal to 6 mm the histologic diagnosis should be determined in the pathology laboratory.