Objective: We aimed to compare the diagnostic performance of transvaginal sonography (TVS), magnetic resonance imaging (MRI), and intraoperative frozen section in the assessment of myometrial invasion and to evaluate intratumoral blood flow in any myometrial invasion with transvaginal Color Doppler ultrasonography (TV-CDU). Methods: This prospective study included 64 women consecutively diagnosed with endometrial carcinoma. The subjects were evaluated by TVS, MRI, and TV-CDU by 2 radiologists with a special training in gynecology. Intraoperatively, a frozen section was obtained and processed for interpretation by a blinded pathologist. Sensitivity, specificity, negative, and positive predictive values were calculated for each imaging modality and frozen section with regard to assessment of myometrial invasion. The intratumoral blood flow was evaluated by TV-CDU. Results: Transvaginal sonography, MRI, and frozen section showed no statistical significant differences in overall diagnostic performance for t e preoperative and intraoperative assessment of any myometrial invasion, although frozen section seemed to be slightly superior to the imaging techniques. The positive rate of intratumoral blood flow was higher in deep myometrial invasion, but statistical significance was not obtained. The mean value of resistance index was significantly lower in the cases with deep myometrial invasion. Conclusions: Transvaginal sonography with concomitant TV-UCD is low-cost, easily performed, and repeated technique for particularly deep myometrial invasion. Because of its high costs and time-consuming, MRI may be recommended in the cases with poor quality of TVS. Because depending solely on imaging methods could lead to insufficient treatment schedules, intraoperative frozen section should also be performed for myometrial assessment. © 2009 by IGCS and ESGO.