Six patients are reported illustrating some of the skull and intracranial manifestations of neurofibromatosis. These lesions, consisting of skull contour changes and various skull bone defects, are sometimes associated with a variety of intracranial tumors. Neurofibromatosis patients with central nervous system tumors usually show few or none of the classic cutaneous marks of the disease. The cases reported here further support the interesting observation of a distinct roentgenologic sign in neurofibromatosis: the local calvarial defect of the left lambdoid suture.