The clinical records of 108 infants presenting with hydrocephalus at birth and operated on from 1971 to 1981 were reviewed in order to evaluate the functional results. Premature newborns and spina bifida patients were excluded. Communicated hydrocephalus (39 cases) and aqueductal stenosis (32 cases, excluding 6 X-linked hydrocephalus and 4 toxoplasmoses) were the two main types of hydrocephalus in this series. Eighty-four percent of the infants were operated on before the age of 3 months. The mean follow-up time was 7 years (range 1 to 14 years). The survival rate, calculated by the life table method, was 62% at 10 years. The functional results were evaluated according to intellectual performance, academic level, and psychological status. Of the 75 surviving children, 28% have an I.Q. over 80 and 50% an I.Q. under 60. The mean I.Q. is 54 (range 0 to 130). Of the 52 children who have now reached school age, only 29% have reached a normal academic level. The psychological status is normal or borderline in 46% of the patients. The importance of head enlargement at birth, ventricular size, and the age at the time of surgery are not related to late functional results. The results were best when there were no associated malformations, no shunt infection, when hydrocephalus was due to aqueductal stenosis (excluding X-linked hydrocephalus and toxoplasmosis), or when the first developmental quotient measured at 6 months was over 80.