Hydrocephalus in the adult may present symptoms of chronic headache, gait disturbance, dementia, or any combination of these symptoms. All known causes of hydrocephalus are represented in cases of adult onset and show the same clinical syndromes. Clinical features, cerebrospinal fluid examination, and electroencephalogram are not reliable means of differentiating hydrocephalus in adults from other conditions presenting similar symptoms. Pneumoencephalography shows a characteristic picture of generalized ventricular enlargement with air in the basilar cisterns which fails to pass over the cerebral convexities. Ventriculoatrial shunt usually completely reverses the neurological symptoms even when these have been present for many years. Four cases of hydrocephalus in adults are presented which illustrate various manifestations of hydrocephalus. Three patients showed remarkable improvement from long periods of neurological disability following ventricular cerebrospinal fluid shunt.