In this study, 78 patients with aqueductal stenosis were submitted to detailed neurodevelopmental assessment with a follow-up of 5-25 years. Sixty-eight percent of patients were categorized as normal; they either attended normal school courses or had regular jobs. Among these, 34% had some motor abnormalities (ataxia, mild hemiparesis, visual disturbances). Twenty-four percent (19 cases) were moderately disabled (trainable retardation) and 8% (6 cases) were severely handicapped. Epilepsy was observed in 13% of the cases. Incidence of recurrent and generalized seizures paralleled neurodevelopmental outcome (5% in normal, 16% in moderately disabled and 50% in severely disabled patients). Endocrine dysfunctions were evident in 28% of the cases and were characterized by precocious or delayed puberty, amenorrhea and somatic underdevelopment. No patient with ventricular enlargement and a cortical mantle width below 20 mm showed a good outcome. Large ventricles were compatible with normal mental development when compensated with a corresponding cranial vault enlargement. In patients with normal mental status and motor abnormalities, long-term CT scan findings revealed the presence of focal brain abnormalities (poroencephaly, brain atrophy, calcifications, extracerebral collections).