In a group of 78 children with hydrocephalus in the first months of life, the level and pattern of intelligence were considered in relation to various parameters and symptoms of their condition. These included demography (age, sex, handedness); early developmental status; symptoms (visual, motor, and seizure); formative pathology; type of hydrocephalus; site of CSF obstruction; extent and configuration of cortical thinning; and shunt treatment. The common outcome of early hydrocephalus is an uneven growth of intelligence during childhood, with nonverbal intelligence developing less well than verbal intelligence. The origin of this selective cognitive deficit is in neither the hydrocephalic condition itself nor its treatment, but rather in the developmental brain anomalies and symptoms to which the hydrocephalic child is prone: In children with aqueduct blocks and intraventricular hydrocephalus, a selectively thin vertex and occipital lobe; in any hydrocephalic child, ocular abnormalities, motor deficits, and seizures.