We report the magnetic resonance imaging (MRI) findings with a paramagnetic enhancement agent (gadopentetate dimeglumine (Gd-DTPA)) in a 70-year-old woman with carcinosarcoma of the uterus. In the present patient, the polypoid portion histologically most abundant in the sarcomatous component was strongly enhanced by Gd-DTPA and was clearly demonstrated with high signal intensities on contrast-enhanced T1-weighted images. We suggest that MRI with Gd-DTPA may be clinically useful for detection of carcinosarcoma, and that any patient having endometrial carcinoma with the polypoid portion, which is more strongly enhanced by Gd-DTPA within the tumor, may be suspected of carcinosarcoma.