Extracranial shunting of cerebrospinal fluid is a well-known neurosurgical procedure for the treatment of normal pressure hydrocephalus. Research indicating reasonable success using this technique has been based primarily on subjective and global neurosurgical opinion. Given that the treatment carries morbidity risks, and that decisions to shunt are related to increasing adaptive functioning, attention must be paid to adequate measurement of surgical outcome. As part of a larger study, we report pre and postsurgical neuropsychological, neuroradiological, and clinical data on hydrocephalic patients, as well as presurgical intracranial pressure data. Prior to shunting, increase in ventricular dilatation and cerebral atrophy were associated with decreased cognitive functioning, gait disturbance, and bladder dysfunction. Following shunting, there were significant improvements in neuropsychological functioning in terms of attention, concentration, verbal and nonverbal memory, language and communication skills, and constructional skills, as well as clinical improvement in gait and bladder functioning. Improvement was related to presurgical dilatation of the temporal horns of the lateral ventricles and mental status, particularly memory functions.