A series of 185 patients operated on with extrathecal shunts for non-neoplastic aqueductal stenosis has been reviewed. The longterm results of 84 of them, followed-up for 2 to 20 years after primary surgery, are illustrated and critically analyzed. This study indicates that a normal mental development or normalization of mental and neurological conditions can be expected in a high percentage of patients after the CSF diversional procedure which nonetheless is still associated with a high percentage of even serious complications.