We observed two patients with stone formation in the renal pelvis two and five years after pyeloplasty. In both cases there was no obstruction of the pyeloureteral junction detectable. We consider the use of Polyglactin (Vicryl) for the pelvis suture as reason for the stone formation. For stone removal we favourite an endoscopic procedure, in which a removal of residuums of the suture is even possible as the verification of the pyeloureteral junction.