Perforation of the urinary bladder is, in most cases, caused by a blunt or penetrative trauma, respectively by an iatrogenic trauma. A spontaneous rupture of the urinary bladder is very rare. In the literature, its relation with alcohol abuse is speculated. Due to their minimal frequency rates, the diagnosis is very difficult and, not uncommonly, the diagosis is verified only upon surgical revision. The authors present two cases of urgent diffuse peritonitis originating from spontaneous perforations of the urinary bladder.