A new angiographic finding in intracranial aneurysms embolized with Matrix coils is described. Two illustrative cases with a well-defined radiolucent separation between the coil mass and the parent artery are presented. To the best of our knowledge, this is the first report in humans of this finding. On the basis of prior histopathologic studies, this finding, which we call the "white-collar sign," may indicate the formation of a thick connective tissue barrier between aneurysm and artery that prevents any further aneurysmal filling.