&NA;During the last 17 years, complete autopsies were performed on 51 patients who died of cerebral glioblastoma, and 14 were found to have dissemination by cerebrospinal fluid (CSF). In these 14 cases of glioma, the extent of intraparenchymal invasion by the primary tumor and the degree of seeding were studied in connection with histological findings and immunohistochemical staining for glial fibrillary acidic protein (GFAP) as the most reliable marker of astrocytic differentiation. From the findings obtained, the cases were divided into two groups. In one group, consisting of 7 gliomas, autopsy revealed intense seeding, despite only slight invasion by the primary tumor. Among these 7 extensively disseminated gliomas, 4 expressed almost no GFAP, 2 contained only a few GFAP‐positive cells, and only 1 displayed an immunohistochemically high degree of astrocytic differentiation. Clinically, 6 of the 7 affected patients developed symptoms attributable to CSF seeding. In the other group consisting of the remaining 7 gliomas, only slight dissemination was seen, despite extensive infiltration of the primary tumor. Each of these 7 gliomas contained many GFAP‐positive cells. None of the affected patients developed symptomatic seeding. This study shows the existence of two clinicopathologically distinct groups of disseminated cerebral glioblastomas and suggests that, regardless of morphological features, glioblastomas showing immunohistochemically poor astrocytic differentiation tend to shed tumor cells more vigorously but are less invasive at the primary site than those with many GFAP‐positive cells. It is also suggested that, as a consequence, the former glioma type produces symptomatic seeding more frequently than the latter type. (Neurosurgery25:533‐540, 1989)