Various surgical procedures in neurosurgery end with cranial vault defects. It is generally believed that the reason for repair of the skull defect is cosmetic or protective. There is evidence, however, that in selected cases neurologic deterioration can be reversed by cranioplasty. In the sinking scalp flap syndrome the deterioration has been thought to be related to the concavity of the skin flap and underlying brain tissue secondary to atmospheric pressure and also to the in-and-out displacement of the brain through the skull defect. Five cases of symptomatic patients after craniectomy are reported, of which all had a neurologic deterioration that was improved by cranioplasty.