Visual function and optic disc appearances were studied in 68 patients conforming to established criteria of benign intracranial hypertension (BIH). The clinical, radiological, and laboratory findings of those patients whose visual field or acuity deteriorated were compared with those who did not deteriorate over an average follow-up of 4.1 years. Definite loss of visual function occurred in 49% of eyes and was severe in 6%. Patients with high grade or atrophic papilledema, or peripapillary subretinal hemorrhage, were significantly more likely to have had deterioration of visual function. Transient obscurations of vision and the presence of optico-ciliary shunts were associated with severe visual loss. Anemia, older age, and high myopia were other risk factors for visual loss. Chronic papilledema may cause progressive visual loss and, for this reason, BIH is not a benign condition; fundal changes and visual function should be carefully monitored.