Our objective was to evaluate the usefulness of MRI including dynamic study in differentiating malignant, mixed mesodermal tumor (MMMT) from endometrial carcinoma (EC). The MR images were reviewed in 4 patients with histologically confirmed MMMT and 11 patients with EC. Flow voids inside and/or around the tumors were seen in 2 patients with MMMT but not in any EC cases. In dynamic studies, all 4 patients with MMMT showed areas of early and persistent marked enhancement similar to that of the myometrium, mixed with areas of gradual and delayed marked enhancement. The portions showing early and persistent enhancement histologically corresponded to predominantly sarcomatous components with prominent vascularity. Ten of 11 ECs did not show such enhancement and only one showed a rapid enhancement in the early phase which was diminished in the delayed phase. The MR imaging with a gadolinium-enhanced dynamic study seems to be useful in differentiating MMMT from EC.