The placenta, normally confined to the decidual lining of the uterine cavity, can in some circumstances invade the muscular wall of the uterus, a condition known as placenta accreta. Less common is placenta increta, in which placental cotyledons become intertwined with the muscular stroma of the uterus. Placenta percreta, in which the trophoblastic tissues penetrate the serosa of the uterus and may extend directly to adjacent structures, is even more rare and is potentially life-threatening. There have been only 10 reports of direct invasion of placenta percreta into the urinary bladder. We review these cases and report 3 recent patients, one of whom was diagnosed pre-operatively by ultrasonography.