One hundred and eight children born with hydrocephalus were reviewed in order to evaluate their neuropsychological development. Premature children and children with spina bifida were excluded. The most frequent types of hydrocephalus were the communicating type (39 cases) and that where the condition is due to stenosis of the aqueduct of Sylvius (32 cases, not counting 6 cases of Bickers-Adams syndrome and 4 cases of toxoplasmosis); 84 per cent of the children were operated upon before the age of 3 months. The mean follow-up period was 7 years (range: 1 to 14 years). The actuarial survival rate at 10 years was 62 per cent. Among the 75 survivors, 28 per cent had an IQ of at least 80 and 50 per cent and IQ lower than 60; 29 per cent of the 52 children who reached school age had normal education. Forty-six per cent of the children showed little or no disorder of behaviour. The head circumference at birth, the size of the cerebral ventricles and the child's age at the time of surgery had no influence on the neuropsychological development. However, the prognosis seemed to be better in cases without associated malformation or infected valve, in those where the hydrocephalus was due to stenosis of the aqueduct of Sylvius (except when related to sex or toxoplasmosis) and when the first IQ evaluated at the age of about 6 months was higher than 80.