In the past, the diagnosis of "growing skull fracture" or "diastatic fracture" has included a subset of injuries better referred to as "cranial burst fracture." Cranial burst fracture, typically associated with severe injury in infants less than 1 year of age, is a closed, widely diastatic skull fracture accompanied by acute cerebral extrusion outside the calvarium. We treated 11 such infants at the LeBonheur Children's Medical Center and 2 at the Children's National Medical Center from January 1986 through December 1994. Infants ranged in age from 1 to 17 months, with an average age of 5.7 months. All presented with marked scalp swelling and a Glasgow Coma Scale score of 10 or less. Twelve had a history consistent with severe injury (motor vehicle accident, 7, abuse 5). The cause of injury in one patient remains unproven. Surgery (reduction of herniated cerebral tissue, repair of large dural laceration, and cranioplasty) was usually performed within 10 days of injury, a time period long enough to assure hemodynamic stability and resolution of acute cerebral swelling, yet sufficiently brief to avoid the chronic changes (scarring, parasitization of scalp vessels by damaged cortex) associated with a "growing skull fracture." Prompt repair of cranial burst fracture may prevent ongoing brain injury such as has been neuropathologically demonstrated in patients with "growing skull fracture." Magnetic resonance imaging establishes the diagnosis of cranial burst fracture in equivocal cases, rendering unnecessary a "waiting period" to see if scalp swelling resolves. Our experience, together with information in the neuropathological and neurosurgical literature, suggests that cranial burst fracture is associated with severe trauma, requires expeditious treatment, and has been underdiagnosed in the past, leading to "growing skull fracture," a condition requiring more extensive surgery.