We report two cases of primary paraganglioma of the urinary bladder. Case 1. A 61-year-old man was hospitalized with the chief complaints of gross hematuria, dysuria and headache. The patient had a history of hypertension. Cystoscopy disclosed a nonpapillary, sessile tumor in the retrotrigonum of the bladder. An attack of paroxysmal hypertension was induced by bimanual palpation of the tumor, and paraganglioma was suspected. Partial cystectomy with staging pelvic lymphadenectomy was performed. Case 2. A 65-year-old man was hospitalized with the chief complaints of gross hematuria and urinary retention. The patient had no history of hypertension. Cystoscopy disclosed a nonpapillary tumor in the right lateral wall of the bladder. Transurethral resection was performed with no cardiovascular complication. Prostatic needle biopsy showed the histological evidence of prostatic adenocarcinoma. Radical retropubic prostatectomy with limited lymphadenectomy was performed. There was no histological evidence of lymph node involvement of paraganglioma or adenocarcinoma. The histological and biochemical examinations revealed a chromaffin positive, functioning and non-malignant tumor in Case 1, and a chromaffin negative, non-functioning and non-malignant tumor in Case 2. In total, 29 cases of primary paraganglioma of the urinary bladder have been so far reported in Japan. The tumor recurrence, multiple or metastases were recorded in 8 of 29 cases (27.6%), mainly in regional lymph node metastases. We recommend lymphadenectomy at the initial operation, irrespective of pathological finding of the primary paraganglioma of the urinary bladder.