Radionuclide cisternography has the ability to show the CSF dynamics and it can be used to differentiate the various forms of hydrocephalus. The authors reviewed 52 cases of RI cisternography by using Tc-99m-DTPA. The following results are obtained. 1. RI cisternography has been used to differentiate 38 cases of communicating hydrocephalus and 13 cases of noncommunicating hydrocephalus. 2. Gradings of communicating hydrocephalus according to Harwood-Nash classification show the zero case of grade 1, 2 cases of grade 2, 10 cases of grade 3 and 26 cases of grade 4 Among these 8 cases of grade 3 and 4 show symptom improvement after shunt operation. RI cisternography of noncommunicating hydrocephalus shows normal finding in 13 cases among but shunt malfunction was identified in 1 cases. 4. 2 cases of porencephalic cyst and 1 cases of arachnoid cyst show accumulation of radioactive-ity at the cyst in delayed scan. In conclusion RI cisternography is useful to differentiate communicating from noncommuni-cating hydrocephalus and to evaluate cerebral atrophic change and circulating disturbance of CSF in combination with Brain CT. The degree of CSF flow disturbance evaluated by RI cisternography can be used to plan the treatment which require shunt operation. RI cisternogra-phy can also be applicable to study the patency of shunt arachnoid cyst porencephalic cyst. and site of CSF leakage.