A bulging fontanel in an infant is generally regarded as a sign of serious central nervous system disease. It may be caused by meningitis, hydrocephalus, cerebral hemorrhage, brain abscess, or tumor. Benign intracranial hypertension, a syndrome of increased intracranial pressure with a normal ventricular system and a cerebrospinal fluid of normal composition, also will produce a bulging fontanel. Hypoparathyroidism,1 hypovitaminosis A,2,3 hypervitaminosis A,4 hypophosphatasia,5 marked anemia,6 chlortetracycline therapy,7 Addison's disease,8 and pulmonary emphysema,9 have been reported as causes of benign intracranial hypertension. Scattered reports 10,11,12 of the association of roseola infantum with a bulging fontanel have appeared in the literature. The following report of 2 cases is being presented as further illustration of this disease as a cause of benign intracranial hypertension.Case 1.\p=m-\A5-month-old white boy was in good health until 3 days prior to admission, when the mother noted that the child had become irritable and cried unless fondled. On the day prior to admission he refused his midday meal and was noted to have a temperature of 103 F. On examination it was learned that the anterior fontanel was bulging.Fever and irritability persisted for another 24 hours and the child was admitted to the hospital.The child's past history was completely normal. The patient had received no medication other than 0.6 cc. of a pediatrie vitamin supplement daily.On admission, the patient's temperature was 102.2 F, blood pressure 80/45, pulse rate 168 per minute, and respiratory rate, 24 per minute.Physical examination revealed an irritable child in no acute distress. The anterior fontanel was tense and bulging even with the child erect and quiet. Slight injection of the posterior pharynx was present. Slight posterior cervical and suboccipital lymphadenopathy was present. The neuro¬ logic examination was completely normal. No papilledema was present. Laboratory Studies.-White cell count was 8,870 ; differential : 27% polymorphonuclear cells, 67% lymphocytes, and 8% monocytes, hemoglobin, 13.3 gm.'%. Urinalysis was normal.Lumbar puncture opening pressure was 220 mm.water ; the fluid was clear and colorless with no white cells and 47 red blood cells, none crenated, per cubic millimeter; protein, 22 mg.%, sugar, 54