It is well known that, in spite of the characteristic ophthalmoscopic findings, the clinical differentiation of papilledema and papillitis presents at times great difficulties. By definition, papilledema, or choked disk, is a noninflammatory swelling of the optic nerve head, while papillitis, also called neuroretinitis, is an inflammatory swelling of the disk and surrounding retina. More than 90 per cent of cases of papilledema are a result of increased intracranial pressure. This increased pressure, if unchecked, may lead not only to blindness but even to death. In cases of tumor or abscess of the brain in which the lesion cannot be localized and for that reason cannot be removed, or when the increased pressure is due to other causes, decompression is absolutely indicated if the peripheral visual fields begin to show constriction, and if medical management, such as the administration of hypertonic salt solutions or of mercury and iodides (even in