The long-term intellectual prognosis of nontumoral hydrocephalus is described: 75% of the population have a full intellectual quotient greater than 70. But often, there is a heterogeneous pattern of the intellectual quotient with a great difference between verbal and performance results because of poor visuospatial skills. Disabilities of syntactical comprehension of language are also encountered. Sex, age, delay before shunting and frequency of shunt complications are not related to intelligence level or pattern. Meningitis and toxoplasmosis often result in a poor intelligence level, but other etiologies do not influence intelligence level or pattern. Visuospatial deficits, attention disorders and language disabilities are independent of the degree of hydrocephalus but are especially encountered when ventricular dilatation persists in spite of the operation.