Leptomeningeal cyst, so-called growing skull fracture, is one of the infrequent but important complications of skull fracture in childhood. The mechanism for production and the essential features of this condition appear to be a skull fracture with underlying dural tear, through which the arachnoid membrane projects out, resulting arachnoid herniation and cyst, aided by the normal pulsations of the growing brain to the fluid in the cyst, resulting in progressive enlargement of the dural defect and progressive erosion of adjacent bone edges. There may be underlying brain laceration as well, resulting in loss of brain substance and enlargement of ventricle, with communication of the cyst with the lateral ventricle. Commonly there are a palpable or visible scalp swelling which has gradually increased in size, or the signs of underlying brain damage which result in focal or hemiparesis. Roentgenographic findings are characteristic and usually permit an accurate diagnosis. There is an irregular defect in the bone, usually with a scalloped, saucerized margin and everted edges. Treatment consists of excision of the cyst and repair of the dural and bony defects. Recently we have treated a typical case of leptomeningeal cyst in a 6-year-old boy with intractable seizure of 3 years' duration.