Primary small cell carcinoma of the urinary bladder is a rare tumor which has the same histological features of small cell carcinoma of lung. These features can be pure small cells or combines with other malignancies such as transitional cell carcinoma, adenocarcinoma or squamous cell carcinoma. Here a urinary bladder small cell carcinoma, combined with high grade transitional cell carcinoma with differentiation of signet-ring type adenocarcinoma and squamous cell carcinoma, is presented.