A 70-year-old man was admitted with slight dyspnea and fever up. The patient had had total cystectomy for urothelial carcinoma of urinary bladder 14 months earlier and had a ureterocutaneostomy. At 2 days after the admission, he had a sudden attack of dyspnea. He was transferred to the intensive care unit, and mechanical ventilation was initiated. The pulmonary arterial pressure was measured at 65/30 mmHg, but the etiology for the pulmonary hypertension was unclear. Although highly suggestive of pulmonary embolism, chest roentgenogram and chest computed tomography (CT) showed clear lung fields. Pulmonary angiography disclosed no evidence of embolism. Despite anticoagulation therapy he died of respiratory failure. Autopsy revealed diffuse microscopic pulmonary tumor embolism with urothelial cacinoma in the pulmonary arterial vasculature. Microscopic pulmonary tumor embolism has rarely been reported with urothelial carcinoma.