A 70-year-old man was admitted with complaint of gross hematuria. Cystoscopy and computed tomography (CT) revealed a 2.5 cm nodular tumor in the urinary bladder. Pathological diagnosis after the transurethral resection of bladder tumor (TURBT) was invasive urothelial cancer with trophoblastic differentiation of pT1. The tumor was positively stained with human chorionic gonadotropin (HCG). The serum HCG level was 12.8 IU/l in the fourth week after TURBT, and it increased to 35.7 IU/l in the 20th week after TURBT. However, radiological examination at this point did not reveal tumor recurrence or metastases. Three months later, the patient coughed up bloody sputum. Lung metastases (up to 2.4 cm) were identified, and they were surgically removed. The pathological specimen consisted of syncytiotrophoblastic giant cells with hemorrhage and necrosis, but no urothelial cancer element. Because the lung and lymph node metastases developed soon after surgery, chemotherapy was planned. Because the patient had impaired renal function with a creatinine clearance of 33.7 ml/min, we selected combination chemotherapy with gemcitabine and oxaliplatin (GEMOX) rather than cisplatin -based chemotherapy. CT after two courses of GEMOX showed stable disease, but HCG levels markedly decreased from 1,240 IU/l to 7.9 IU/l. This marker of response continued through six courses of GEMOX. Then, the chemotherapy was discontinued due to grade 2 neuropathy. He died of cancer 12 months after development of metastases. Autopsy revealed only tumor cells with trophoblastic differentiation, but no urothelial carcinoma in multiple metastatic sites.