A 51/2-month-old infant had the single problem of a bulging fontanelle. A diagnosis of cystic fibrosis with secondary hypovitaminosis A was made by the findings of high sweat chloride values and a low serum carotene level. A greatly accelerated rate of weight gain following the addition of pancreatic enzyme supplements confirmed the presence of malabsorption. The infant developed characteristic fibrosis pulmonary disease at 20 months of age. Animal studies have shown vitamin A deficiency to be associated with increased cerebrospinal fluid (CSF) pressure, diminished absorption of CSF, and pathological findings of thickening and infiltration with mucopolysaccharides of the dura mater around the arachnoid villi.