During the period from November 1982 to April 1986, a radioisotope cisternography was conducted on 29 patients with hydrocephalus at Seoul National University Hospital, and a ventriculoperitoneal shunting was performed on 15 patients. To correlate the preoperative radioisotope cisternography patterns with the results of ventriculoperitoneal shunting, we classified the radioisotope cisternography findings into five patterns and compared them with the surgical results. The cisternographic patterns are as follows: Type I: No ventricular activity, normal migration, Type II: No ventricular activity, delayed migration, Type III-A: Transient ventricular activity, clearance by usual migration, Type III-B: Transient ventricular activity, clearance without usual migration, Type IV: Persistent ventricular activity, inadequate clerance. All patients operated on were Type III(seven patients) or Type IV(eight patients). Of the eight Type IV patients, seven (88%) showed clinical improvements within two weeks after the shunting, while an improvement occurred in only one (14%) of seven Type III patients. We have concluded that when there is a prolonged ventricular retention of the isotope, the surgical shunting is successful suggesting that the radioisotope cisternography has a significant preoperative prognostic value.