This study evaluated the accuracy of magnetic resonance imaging (MRI) and transvaginal ultrasonography (TVUS) in preoperative detection of myometrial invasion by endometrial cancer. We also evaluated the results of gross visual inspection (GVI) of surgical specimens compared with histopathological diagnosis. One hundred and seventy-seven women underwent preoperative pelvic MRI, TVUS, and intraoperative GVI Myometrial tumor invasion was evaluated histologically and classified as absent (depth a), superficial (depth b: <= 50% invasion), or deep (depth c: > 50% invasion). The accuracy of MRI, TVUS, and GVI were 64.0, 66.9, and 63.8%, respectively. The positive predictive values of of each modality for depth a were 52.6, 51.4, and 52.2%, respectively. The accuracy of each in detecting deep myometrial invasion (depth c) were 84.0, 86.9, 83. 1 %. Although evaluation of depth a was limited with all modalities, MRI and TVUS were shown to be reliable for preoperative evaluation of deep myometrial invasion. The high accuracy of these three methods suggests that they are useful either interchangeably or in combination.