Ureterocele without corresponding renal tissue (blind ureterocele) represents a very rare malformation which is of special interest for the understanding of the embryogenesis of this anomaly. Two cases, the first without corresponding kidney seen in an adult and the second in connection with a small multicystic kidney observed in a boy, are considered. In light of the observation of the disappearance of antenatally diagnosed multicystic kidney, these lesions are considered to represent two different stages of the same anomaly. A somewhat functioning renal tissue is supposed to be necessary for the development of a ureterocele. In the case of blind ureterocele, it is supposed that the renal tissue might subsequently disappear. Ureterocele may result from a combined ureteral bud anomaly and obstruction during fetal development.