Using standard cerebral computerized tomography (CT), we diagnosed pseudotumor cerebri (PTC) and correlated the CT findings with CSF pressure and severity of visual impairment. 13 patients with a clinical diagnosis of PTC were compared with 20 age-matched controls with headache, but without papilledema or other neurologic signs. Cerebral CT consisted of axial sections of the posterior fossa, including the orbits. In all subjects the diameter of the optic nerve sheath, reversal of the optic nerve head, presence of empty sella, and size of the ventricles, cisterns and sulci were evaluated. There were no differences in basal cisterns and ventricles between those with PTC and control subjects. Empty sella was found in 6 of 13 PTC patients, compared with 1 of the 20 controls. Optic nerve sheath diameter in controls ranged from 3.5-5.0 mm (average 4.2 +/- 0.54 mm) but from 4.5-9.0 mm (average 6.8 +/- 1.54 mm) in those with PTC. Reversal of the optic nerve head was seen in 4 cases of PTC but in none of the controls. In PTC patients with opening CSF pressure greater than 270 mm water, the diameter of the optic nerve was wider than 7.5 mm. Thus, in most cases of PTC, bilateral enlarged optic nerves can be measured by standard cerebral CT and intracranial space-occupying lesions can be excluded as well. Moreover, reversal of optic nerve head, and empty sella can frequently be seen on CT in those with PTC.