Twelve cases of cerebellar astrocytoma experienced in the Department of Neurosurgery, Hokkaido University School of Medicine were examined primarily for tumor stain and pathological tumor circulation by angiography. In addition, comparison on neuroradiological findings between cerebellar astrocytoma and hemispheric supratentorial astrocytoma (low-grade) was carried out, and neuroradiological differential diagnosis of cerebellar astrocytoma and cerebellar hemangioblastoma was discussed on the basis of the present results and those which were already reported by other investigations and the authors. The results are as follows: 1) Tumor stain was observed in only one case. A tumor was demonstrated as an avascular mass in the remaining 12 cases. 2) Demonstration of cerebellar astrocytoma as hypovascular or avascular masses was related to their low-grade malignancy in histology and cystic nature in gross appearance, as already pointed out. Furthermore, the present study suggested that mural nodules of cystic lesions should have certain weight and sizes so that they could be demonstrated as tumor stain. 3) Abnormal findings concerning tumor circulation were mostly limited to the cases with tumor stain. Early filling veins were not found in any case. Neither feeding artery nor draining vein was clearly identified in some cases. In addition, the abnormal vessels lacked hypertrophic and tortuous changes. 4) In the supratentorial region, five of the 12 low-grade astrocytoma exhibited abnormal tumor stain and tumor circulation by cerebral angiogram and we think that supratentorial and posterior fossa astrocytoma must usually exhibit different pathological tumor circulation by cerebral angiogram, since each group has distinctive clinical and biological characteristics. 5) CT was performed in 7 of 13 cases. It appeared to be more useful than cerebral angiography in the morphological diagnosis Especially in cystic tumors, CT produced minute information concerning peritumoral edema, enhancement of margin of cystic astrocytoma after intravenous contrast medium, and marginal enhancement with layering in the dependent part of the cyst. 6) Neuroradiological different diagnosis of cerebellar astrocytoma and cerebellar hemangioblastoma by CT was difficult in our cases of cystic tumors. However, both tumors were differentiated from each other with ease by tumor stain and tumor circulation in cerebral angiography, since cerebellar astrocytoma was lacking in abnormal vessels, whereas cerebellar hemangioblastoma was marked by many abnormal vessels. Thus, we concluded that cerebral angiography is superior to CT in differential diagnosis between cerebellar astrocytoma and cerebellar hemangioblastoma.