A case of malignant mixed mesodermal tumor (MMMT) developed after radiation therapy for a uterine cervix cancer is described. The patient was a 62-year-old female at the time of diagnosis of stage Ib squamous cell carcinoma of the cervix and a total of 12,000 rads of x-ray was administered on the pelvic area. Five years later she manifested vaginal spotting and rectal pain. Endometial curettage and biopsy revealed carcinosarcoma. Radical hysterectomy was done and a 5x3x2 cm sized polypoid mass was noted in the uterine cavity. Microscopically, the tumor showed intimate admixture of adenocarcinomatous and sarcomatous areas. The sarcomatous stroma was composed of compactly arranged atypical spindle cells with frequent mitoses, merging into a loosely textured reticular areas and abundant amount of heterologous elements such as skeletal muscle and cartilage. The rhabdomyosarcomatous element was confirmed by PTAH staining and immunohistochemical staining for myoglobin and desmin. Multiple metastases to the liver, lung, and lymph nodes appeared within one year of total abdominal hysterectomy and bilateral salpingo-oophorectomy. In spite of palliative radiotherapy, she expired one month later.