[en] The correlation between the findings on MR images and CT findings, clinical symptoms, and the results of various specific investigations was determined. MR imaging was more sensitive in demonstrating the pathology of the periventricular tissue in hydrocephalus than was CT scanning, although the overall correlation between MR and CT findings was good. The authors classified the periventricular high-signal intensities (PVHI) of MR images into 4 types according to the extension and grade of the PVHI. Type 0 has no PVHI. Type I has a band of the PVHI around the wall of the lateral ventricles, including the corpus callosum and the septum pellucidum. In Type III, PVHI extended half of the width of the periventricular white matter, while in Type IV PVHI occupied the entire white matter. CT scans showed periventricular lucency (PVL) only in the periventricular white matter, especially surrounding the anterior horn, but the PVHI was visible not only in wider areas of the entire periventricular white matter, but also in the corpus callosum and the septum pellucidum. The PVHI seen in case of hydrocephalus due to posterior fossa tumors was characterized by PVHI of Type I; the PVHI disappeared after CSF shunting in all cases. There was no PVHI in the cases of marked hydrocephalus due to aqueductal stenosis, which appeared to be compensated for a long period. In the cases of normal-pressure hydrocephalus, there were various types of PVHI. There was no correlation between the types of PVHI and the grade of ventriculomegaly. There was, however, a close correlation between the types of PVHI on MR images and the clinical symptoms, and the cerebral blood flow in cases of normal-pressure hydrocephalus. In some patients with normal-pressure hydrocephalus, the PVHI improved and the cerebral blood flow increased after cerebrospinal fluid shunting. (J.P.N.)