A 59 year-old man, previously healthy first visited our urological clinic on February 25, 1974, with 2-month old intermittent asymptomatic gross hematuria. Urethrocystoscopy revealed a slight stenosis on the membranous urethra and a hen's egg size solid tumor was found on the left lateral wall of the urinary bladder by cystoscopic optics. The mucosa of other parts of the urinary bladder was without remarkable change and the right ureteral orifice was normal. However, a left ureteral orifice was not found because of the infiltration of the tumor. On March 17, 1974, the patient was admitted to our hospital for treatment.<br>Excretory urogram revealed a delay of excretion and a dilatation of the upper urinary tract on the left side in contrast to the right side. A large round defect of the contrast medium at the left lateral side of the urinary bladder was seen by excretory cystography. Pelvic angiography using air cystography for negative contrast revealed abnormal tumor vessels and tumor stain. There was no sign for the metastatic changes in the lungs, gastrointestinal tract and lymphnode by other radiological examinations. Urinary exfoliative cytologic examinations were performed several times using the Papanicolaou stain and the cytologic diagnosis was always transitional cell carcinoma class IV or V. Laboratory tests, including hemograms, serum electrolytes, blood urea nitrogen, creatinine, glucose, calcium, phosphate, serum proteins were normal. An isotope liver scan was normal. The patient underwent a total cystectomy with an ileal conduit as an urinary diversion.<br>Grossly, the tumor was solid and well circumscribed, but there were areas of hemorrhage and necrosis on the surface of tumor. Histologically the tumor tissue was composed of anastomosing trabeculae, ribbonlike structures occasionally forming rosettes structure. Histochemically, the tumor cells were positive for the argyrophil reaction by Grimelius silver stains. Furthermore, the tumor cells had charac-teristic uniform, round, membrane-bound granules by electronmicroscopic examinations. From these results the pathological diagnosis of this tumor was determined as a primary carcinoid tumor of the urinary bladder.<br>Roentgenographic examinations of chest skeletal system and entire alimentary tract after the operation were normal. The excretory urogram was normal and the delaying of excretion and dilatation of the upper urinary tract on the left side was improved. Serum serotonin level was slightly elevated (42.2mcg/dl), but 24 hour excretion of urinary 5-hydroxyindol acetic acid was within normal limits. Laboratory tests after the operation were also normal.<br>One month after the operation the patient was discharged from the hospital under healthy condition without metastatic sign. The patient was examined monthly for routine follow up and received orally N₁-(2-tetrahydrofuryl)-5-fluorouracil treatment. Five months after the operation the patient complained of a small tumor formation with pain in the perineum. An extirpation of this tumor and the histologic diagnosis was metastatic carcinoid tumor. After the extirpation of the tumor the perineal pain disappeared immediately. At that time the patient was very healthy the radiologic examinotions and the laboratory tests were within normal limits.<br>Nine months after the operation the patient was found to have a round lung metastasis in the right lower lobe by chest radiological examination. At that time he complained of sweating and weakness 2 months in duration. The patient received intravenously N₁-(2-tetrahydrofuryl)-5-fluorouracil treatment. However, the metastatic lesion spread immediately in the both lungs and the clinical course of the patient was rapidly downhill. The patient died in March 1976. Autopsy was not performed.