In a review of the cases of diverticulum of the urinary bladder observed in the urologic clinic of the Peter Bent Brigham Hospital, there are several points with which I have been especially impressed, perhaps, most of all by the frequent association of neoplasm and calculus of the bladder with diverticulum. Thirty-one cases of diverticulum of the bladder were reviewed. In this group there was a sac of not less than 2 cm. in diameter in every case. In ten cases, or 30 per cent, there were multiple diverticula; in five others, the records mention the presence of additional cellules or saccules, varying in size up to 0.75 cm. in depth. Diverticulum of the bladder is predominantly a disease of men. Only one case occurred in a woman, and this was not recognized before operation. In this case the sac was similar to those observed in men; it opened on