BACKGROUND The aim of this study was to determine the efficiency of transvaginal ultrasonography in the assessment of myometrial invasion and cervical involvement (preoperative staging) of endometrial cancer. METHODS Transvaginal ultrasonography was performed on 52 women to classify endometrial cancer with respect to myometrial invasion and cervical involvement according to the International Federation of Gynaecologists and Obstetricians recommendations for surgical staging of endometrial cancer. Endometrial cancer was diagnosed on the basis of dilatation and curettage and the degree of invasion was evaluated preoperatively by transvaginal ultrasonography. Ultrasonographic findings were compared to the surgical staging and histopathology of the surgical specimen. RESULTS Myometrial invasion evaluated by transvaginal sonography was accurate in 46 of 52 cases (accuracy 88%, sensitivity 86%, specificity 90%, positive predictive value 92%, negative predictive value 83%). Tumor extension to the cervix was properly diagnosed in seven of ten women in which it was present. CONCLUSIONS Transvaginal ultrasonography is a reliable method for assessing myometrial invasion and cervical involvement. This non-invasive method should be included as an important tool in the establishment of individualized treatment programs for women with endometrial cancer.