The over the wire occlusion balloon catheter is a new interventional neuroradiology tool. We present two cases where this system was crucial for the management. In the first case it allowed us to perform an occlusion test before closing in safe conditions a M2 fusiform aneurysm. In the second case, it allowed us to control a subarachnoid bleeding after endovascular perforation of a normal left P1 segment. We believe that all interventional neuroradiologists should be familiar and comfortable with the systems available.