A 59-year-old male took total cystourethrectomy on July, 1991, since the bladder tumor recurred 2 years and 4 months after transurethral resection. Six months after total cystourethrectomy, an abnormal mass shadow appeared on the right lower lung field. Metastatic lung tumor was strongly suspected from CT scan. Despite chemotherapy, the pulmonary lesion grew rapidly and the patient died. From the autopsy, metastatic lesions were found in the bilateral lung fields, skin (face, head and abdominal wall), pleura, bilateral kidneys, small intestine and lymph nodes (para-aortic and mesenteric). The primary bladder tumor contained histologically transitional cell carcinoma as the epithelial element and sarcomatous changes with osteoid formation as the non-epithelial elements. Thus, the primary lesion was diagnosed as a malignant mesodermal mixed tumor. However, all of the metastatic lesions showed only sarcomatous changes. Only 10 cases of malignant mesodermal mixed tumor of the bladder have been reported in Japan since Fujita's report. In general, total cystectomy is necessary for the treatment of this disease. It has a poor prognosis; 5 of the 10 patients died within one year after operation.