This Hoyt lecture is composed of 2 topics. First, a series of patients with idiopathic intracranial hypertension (IIH) is presented, emphasizing the importance of magnetic resonance venography (MRV). Study of the cerebral venous sinuses in IIH may demonstrate focal stenosis or venous gaps and represent a manifestation of elevated intracranial pressure. Conversely, the clinical picture of IIH may occur following cerebral venous sinus thrombosis, and MRV may be essential in establishing this diagnosis. In the future, evaluation of flow in the cerebral venous sinuses may play an important role in determining the potential for visual failure. Second, I will review patients with visual cognitive changes, which often go unrecognized. These patients suffer from visuoperceptual disturbances, recognizing parts of visual scenes but not the entire picture and are unable to comprehend their visual environment. These findings are often part of the syndrome of posterior cortical atrophy characterized by parieto-occipital atrophy, enlargement of the atrial portion of the ventricular system, and diminished metabolic activity in the posterior portion of the brain demonstrated with positron emission tomography.