The development of a leptomeningeal cyst following an otherwise uncomplicated linear skull fracture in a young child may result in a sizable cranial defect and irreversible neurological deficit months or years later. This complication most often follows parietal fractures but is also seen after occipital fractures or traumatic suture diastases. An underlying dural tear is a prerequisite to its subsequent development. Neurological deficit may be avoided by early diagnosis, surgical excision, dural closure, and cranioplasty. Early diagnosis depends on obtaining a skull roentgenogram four to six months following the original injury in any child where examination of the scalp and skull suggests and underlying expanding fracture.