RESUMEN
Since the discovery of CT scan for brain, the detection of hydrocephalus became easier than before. Of those hydrocephalus, non-parenchymatous in origin, in order words, normal pressure hydrocephalus can be differentiated by RISA cisternography. The etiology, symptomatology and surgical outcome of 16 cases of normal pressure hydrocephalus were presented. Followings are the results. 1) All of the cases revealed ventriculomegaly in brain CT scan and prolonged ventricular retention of dye in RISA cisternogram. 2) Ventriculoperitoneal shunt was done on all of the patients and outcome was excellent:3, good:6, fair:3 and poor:4. 3) It is thought that the prognosis is much related duration of clinical manifestation; the earlier surgery, the better outcome.